This article is updated regularly as events unfold.
The United Kingdom is due to leave the European Union — an economic and political partnership of 28 countries — bringing to an end 46 years of British membership.
Brexit is set to be the most important constitutional shake-up the UK has known since it joined the six-nation European Economic Community in 1973, and represents the first time the European institution has lost a member.
The process has plunged the UK into its worst political and constitutional crisis since the Second World War. The country had been due to leave the EU on March 29, 2019, but the revised departure date is now October 31 after gridlock in parliament twice forced an extension.
It was followed by a summer of further British political turmoil — which saw Boris Johnson replace Theresa May as Conservative prime minister.
The EU and UK announced on October 17 that they had reached agreement on a revised Brexit deal. It was swiftly approved by EU national leaders.
However, the deal needs the approval of the British and European parliaments and the outcome is still uncertain.
The UK voted to leave the EU by 52% to 48% in June 2016. The result has increased strains between the UK's individual countries: England (53%) and Wales (52.5%) voted to leave, whereas Scotland and Northern Ireland voted by 62% and 56% respectively to remain in the EU.
Brexit has been described as largely an English nationalist project, although factors such as austerity and frustration with traditional politics undoubtedly come into play. It feeds into a wider debate concerning the role of the nation state and the rise of populism in an age of globalisation. Many are concerned that it has shifted attention from major global challenges, not least the battle to contain climate change.
For many in Europe, the prospect of an institutionalised rift between the UK and the EU weakens the continent at a time when the likes of America, China and Russia are becoming increasingly assertive.
Latest developments and stories (to October 18):
Brexit on a knife-edge after EU and UK strike new deal
After a dramatic race against the clock, the EU and the UK announced on Thursday (October 17) that they had reached agreement on a revised exit deal.
It came on the day of a crucial EU summit and followed a period of intensified talks in the weeks before the UK's scheduled departure date at the end of October.
But the agreement still needs the support of British lawmakers and the European Parliament. UK MPs will sit on Saturday and vote on whether to back it. Boris Johnson's Conservatives have no parliamentary majority and projections suggest a very tight contest — especially given the opposition of key Northern Irish unionists.
The parliamentary session promises to be one of the most dramatic in decades. The House of Commons — meeting on a Saturday for the first time since 1982 — will be setting the country's direction for years to come.
If the vote is passed at Westminster, the race will be on to pass the necessary legislation and ratify the accord ahead of the Halloween deadline.
If it fails, UK law compels the prime minister to seek another Brexit extension from the EU.
What's in the new deal?
The main change is that the controversial Irish "backstop" contained in the previous Withdrawal Agreement is scrapped. To keep an open border on the island of Ireland, it envisaged an insurance policy where — in the absence of a trade deal or another solution — the UK would remain in the EU's customs union.
Instead, under the new deal Northern Ireland would leave the customs union with the rest of the UK, which wants to pursue its own trade deals. But in practice it would follow EU customs rules and be subject to EU oversight.
The North would remain aligned with some aspects of the EU's single market — and apply EU law on VAT (Value Added Tax) rules.
Customs and regulatory checks would not be carried out on the island of Ireland, but at ports — effectively creating a new regulatory divide in the Irish Sea.
The agreement has similarities with an original EU proposal for a Northern Ireland-only backstop — which was rejected by Theresa May's government — but is more complex, and has one key difference in that Northern Ireland would be legally in the UK customs union.
The accord deals with the issue of Northern Irish consent for these changes: Northern Ireland's assembly would be able to decide on whether to keep the new arrangements — but only four years after a planned transition period.
The revised withdrawal agreement keeps its existing provisions on settling the UK's financial obligations to the EU, and one safeguarding citizens' rights — those of EU nationals living in the UK and Britons in the EU (see below). These will come into force if the deal is ratified.
- Click here to read more about what's in the new deal — see also the full text of the revised section.
Boris Johnson also signed up to a "level playing field" with the EU over issues including state aid, competition, social and workers' rights, the environment and climate change. However, this engagement is included in the Political Declaration — which is legally non-binding — rather than the withdrawal agreement which would have the force of an international treaty.
The political declaration concerns future EU-UK relations, and is causing concern among some Brexit opponents — especially given the Johnson government's avowed intention to diverge from EU rules and forge an independent trading path.
- See the revised text of the 27-page Political Declaration.
From near-breakdown to breakthrough: how was the deal done?
In a nutshell, Boris Johnson made major concessions over Northern Ireland. The EU also gave ground, re-opening the withdrawal agreement it had always said was sacrosanct.
Gone are the UK's proposals — much vaunted by Brexit supporters — for "alternative arrangements" including technological solutions to keep an invisible border. Instead, Johnson has agreed to a different status for Northern Ireland compared to the rest of the UK — accepting a plan very close to one the EU originally proposed.
Ireland and the EU also moved — agreeing to replace the backstop, and opening the door to a possible time-limit on border safeguards with the new consent mechanism.
Border issues unblocked
Ahead of the key EU summit on October 17-18, hopes were suddenly revived that agreement might — just — be achievable between the UK and the EU. The positive mood followed a meeting between UK Prime Minister Boris Johnson and his Irish counterpart Leo Varadkar.
The details were kept under wraps, but Brussels responded to new compromise proposals from London on customs arrangements on the island of Ireland. But while agreement was close on the eve of the summit, Johnson faced resistance to the reported plans from allies at home. Northern Ireland's Democratic Unionist Party (DUP) said it could not support the proposals "as things stand".
Ten days earlier, talks between London and Brussels all but collapsed amid an outburst of acrimony, with both sides blaming each other.
Arrangements for Northern Ireland have been a key sticking point throughout negotiations ever since the UK triggered the formal Brexit process in March 2017. Behind the details over trading arrangements are fundamental questions concerning identity. The possibility of new borders — between Northern Ireland and either the Irish Republic, or Great Britain, or both — are hugely problematic in a region with a troubled past.
After months of political and constitutional turmoil in the United Kingdom, the British prime minister finally submitted a new Brexit plan to the European Commission in early October. But it quickly became clear that huge gaps remained in their respective positions.
Boris Johnson’s plan amounted to a radical overhaul of the divorce agreement negotiated by Theresa May's government. The Irish border "backstop" — the main sticking point throughout the talks – would be stripped out.
Under the British proposal as originally tabled, no longer would the UK remain in a customs union with the EU — the backup measure to guarantee an open border on the island of Ireland in the absence of a trade deal or an alternative solution. Northern Ireland would leave the EU’s customs union along with the rest of the UK — but would remain partially aligned to EU single market rules, subject to approval by Belfast every four years.
The prime minister’s assurances over customs checks in the politically sensitive region failed to convince EU leaders, citing a 1998 peace accord. The proposals over the single market and consent also caused alarm — not least among many in Northern Ireland’s business and farming communities.
Following the Johnson-Varadkar meeting, reports subsequently suggested the UK had shifted to accepting a dual customs regime. The EU responded positively, but details of a revised agreement remained elusive as talks took place behind closed doors.
The European Council summit of EU leaders on October 17—18 had been seen as a crucial date. Any new agreement would have to be submitted to and approved by leaders of the 27 other EU countries.
A deal was indeed done. However, many obstacles remain if Brexit is to happen by October 31. The full text and accompanying legislation must be passed at Westminster — and the deal must also be passed by the European parliament — all before the end of the month.
October 17—18: the last scheduled European Council summit before Brexit day.
October 19: UK parliament to hold emergency session in first Saturday sitting since 1982.
October 31: the date when the UK is due to leave the EU.
Could a no-deal Brexit still happen?
Despite the new EU-UK agreement, approved by EU27 countries, the deal still needs to be passed by the UK and European parliaments.
Unless that process is completed on time, then in the absence of any other intervention the default legal position is that the UK will leave the EU on October 31.
Boris Johnson has repeatedly said he is determined to respect that deadline and take the UK out of the EU without a deal if necessary — a stance which won strong support among Conservative Party members, but which many say would be disastrous.
Another showdown beckons between the UK government and lawmakers, when parliament meets for an emergency Saturday session on Saturday (October 19). The previous withdrawal deal was rejected three times by the House of Commons, and safe passage for any new deal is far from assured.
Meanwhile, a majority In parliament are opposed to a no-deal Brexit. A law has been passed to try to force another delay to prevent such a scenario.
The new law known as the Benn Act obliges Johnson to write to the EU asking for a three-month extension until January 31, unless parliament has either approved a deal or consented by October 19 to leave without one. The British government has said it will adhere to the law, while vowing to test what it describes as a “Surrender Act” to the limit.
Some observers believe that Johnson's hand would be forced by the law. Opponents of no-deal are divided, however, between those who want the UK to leave the EU with a deal, and those who want to stop Brexit.
EU countries would have to agree unanimously to another Brexit extension for it to take effect. In April some countries, led by France, argued for only a short delay and might be even more reticent to prolong the UK's EU membership another time.
The EU — unlikely to want to be seen to be expelling the UK — is thought likely to grant an extension if requested, albeit perhaps attached to conditions. The European Parliament has voted to support a Brexit extension should the UK ask for one.
Supporters of a second EU referendum are expected to move at some stage, to try to put any deal to another public vote in a second referendum.
'Do or die': Boris Johnson's drive to seal Brexit
The UK's stance towards Brexit took on a distinctly harder edge when Boris Johnson entered Number 10 Downing Street, raising the likelihood that the country will leave the EU without a withdrawal deal.
The former foreign secretary and London mayor took over the reins after winning the Conservative Party leadership contest. He signalled immediately a reinvigorated drive to take the UK out of the EU on October 31, "no ifs or buts", and appointing prominent Brexiteers to key posts in his new cabinet.
The prime minister has said flatly that he will not extend Brexit — he would rather be "dead in a ditch" — insisting that "the UK will come out anyway" even if no deal is struck.
Johnson says he wants to negotiate a new withdrawal agreement with the European Union. After sending his new Brexit plan to Brussels, the prime minister called on the EU to follow his lead and compromise. But his opponents allege his purported drive for a deal is camouflage, and that in the circumstances his real goal is a no-deal Brexit.
'Get Brexit done'
The UK government has significantly ramped up its no-deal preparations, with more funds promised. The Conservative conference in Manchester had a new slogan, “Get Brexit done” — which has echoes of the “take back control” rallying cry of the “Leave” campaign during the 2016 referendum campaign. Opinion polls have suggested the Tories still command a significant lead over opposition parties.
Their critics argue that far from settling Brexit, leaving the EU without a deal would resolve nothing – bringing only economic chaos and a new era of uncertainty.
'Ditch the backstop'
Upon taking office in July, the new prime minister took some by surprise with a demand for the Irish backstop to be removed from the negotiated withdrawal deal — a demand that was quickly rebuffed by the EU. Johnson followed up with a formal plea in August, arguing that the backstop is anti-democratic and inconsistent with UK sovereignty.
The backstop was essentially an insurance policy to avoid a hard border — such as border posts — and protect the cross-frontier economy between Northern Ireland (part of the UK) and the Republic of Ireland (part of the EU), post-Brexit. In the absence of a free trade deal it would have kept the UK close — and Northern Ireland even closer — to the EU.
Theresa May's withdrawal deal was negotiated by London and Brussels over an 18-month period and approved by the 27 other EU governments in November 2018 — before being rejected three times by the British parliament.
Running parallel to the Brexit saga has been the UK's evolving relationship with the United States, with which Britain hopes to strike a future trade deal. Boris Johnson met President Donald Trump at a G7 summit and admitted talks would be tough. Trade experts say the UK faces a key choice over regulatory alignment: whether to stay close to EU rules to access the European market, or follow American regulation.
What would happen in a 'no-deal scenario'?
The new EU-UK accord makes a no-deal Brexit less likely — but the ratification process still faces significant hurdles, not least at Westminster.
Although many expect another extension to the UK's EU membership, Johnson's government is fiercely opposed to such a scenario. The default legal position is that the UK will leave the EU on October 31, with or without a deal.
Should the United Kingdom leave the European Union without an approved exit deal, legal arrangements covering many aspects of everyday life — including the rights of British and European citizens — would abruptly cease to apply. It would also bring an immediate change in the trading relationship between the UK and the EU.
Although some believe the fallout would quickly force both sides back to the negotiating table, relations would be further damaged — especially if the UK refused to pay its "divorce bill", as Boris Johnson threatened to do.
A "no-deal" Brexit would hit the UK's economy but also those of its closest neighbours on the continent — and particularly the island of Ireland, where the survival of a hard-fought peace accord is at stake after decades of political violence.
Many political leaders, institutions, companies and individuals have warned of severe disruption and economic damage on both sides of the English Channel — with the UK being hit worse than the EU.
However, Brexiteers have long dismissed “Project Fear” forecasts and some argue that the UK could survive perfectly well under World Trade Organisation (WTO) rules.
Government documents, published in early September and codenamed "Operation Yellowhammer", confirmed a grim assessment of the potential impact of a no-deal scenario. Based on the government's own preparations for a no-deal Brexit in a "worst case" scenario, they contained warnings of possible food, medicine and fuel shortages.
The heightened uncertainty amid a winter of British political turmoil forced the UK and the EU, as well as people and businesses on both sides of the English Channel, to step up no-deal preparations ahead of the original March deadline — plans that were revived in the run-up to October 31.
In March the European Commission said it had completed its no-deal preparations, having released its Contingency Action Plan for Brexit in December. In a no-deal scenario, it confirms that the rights of EU citizens living in the UK and Britons on the continent would no longer be protected at European level — and lays out basic plans to regulate financial services, air transport, road haulage, customs and exports, and climate policy.
Theresa May's government published a series of papers — some updated under her successor — advising UK citizens and businesses on the consequences and how to prepare for no-deal. It said the EU would treat the UK as a "third country", and there would be no agreement on applying arrangements set out in the exit deal.
British economic sectors reliant on close, smooth arrangements with Europe have warned of the dangers of new costs and restrictions being imposed overnight. Among those sounding alarm bells are manufacturing industries — including the car industry, food and drink, chemicals and pharmaceuticals – as well as aviation, the health service, tourism, and financial services. There have also been warnings over farming and fishing — despite strong support for Brexit from within these two sectors.
Brexit and business — read more:
As the process dragged on without formal approval for an exit deal from the UK and EU parliaments, the focus shifted even more sharply to “no deal” preparations.
In August 2019, after the Bank of England lowered its growth forecast for the UK post-Brexit, its governor Mark Carney warned that in the event of no deal the economy would suffer an instant hit, prices would rise and the pound would fall, and even large profitable industries would become "uneconomic".
In April a leaked letter by the government's most senior civil servant warned of an economic recession, food price rises, a severe impact on Britain's security services, police forces and legal system, and a return to direct rule by the UK government in Northern Ireland. In early August a leaked government document contained similar warnings.
In June, the same civil servant, Sir Mark Sedwill, said government and public services were in "pretty good shape" to cope with a no-deal Brexit at the end of October. He added that in the private sector the level of preparedness varied from sector to sector.
In November 2018, two major reports by the UK Treasury and the Bank of England assessed the potential damage to the British economy of various Brexit scenarios.
In its assessment of EU preparations for no-deal, the UK House of Commons Library describes the Commission's programme as one of "damage limitation" to protect the EU27 countries.
The UK's Brexit turmoil: constitutional storm as parliament suspension ruled unlawful
The UK’s new prime minister suffered a humiliating defeat when the country’s highest court ruled that his government had acted unlawfully in early September by suspending parliament for five weeks.
The 11 judges in the Supreme Court ruled unanimously that the decision to prorogue parliament unlawfully prevented it from carrying out its constitutional role without good reason, and was null and void.
Boris Johnson argued at the time that the move had nothing to do with Brexit, and was standard procedure to allow the government formally to set out its agenda in a new parliamentary session.
The government’s opponents had argued the prorogation was intended to muzzle them over Brexit and ensure the UK left the EU on October 31.
The court’s ruling represents a significant check on executive power by the judiciary, and has severely tested the United Kingdom’s unwritten constitution. The country is deeply divided not just over its future in Europe, but also over the nature of its democracy — with defenders of parliamentary representation pitted against supporters of "direct democracy" as embodied by the EU referendum.
Johnson — resisting calls to resign — said he strongly disagreed with the judgement but respected the independence of the courts. Parliament resumed the following day amid rancorous scenes, but the impact of the Supreme Court ruling on Brexit itself is uncertain.
The prime minister lost his majority in the House of Commons after expelling more than 20 Conservative MPs who rebelled against the government's no-deal stance.
Lawmakers have also rejected Johnson's bid to call an early general election, until an extension to the UK's EU membership is secured.
How we got here: Brexit delay brings European election electroshock
Johnson's arrival in No 10 Downing Street followed a prolonged period of turmoil in British politics. This came to a head when Theresa May — who failed to get her EU divorce deal through parliament — became the latest in a long line of Conservative prime ministers to be brought down by Europe.
In the wake of the repeated parliamentary defeats for the EU divorce deal, the House of Commons twice forced the British government to seek to delay Brexit. EU national leaders met for a special European Council summit on April 10 and agreed to a six-month "flexible extension" to the UK's departure from the bloc, with a new exit date set for October 31 — or earlier if its parliament approved the original withdrawal deal.
But the extension of the UK's EU membership forced the country to take part in the European Parliament elections in May — and send 73 newly-elected MEPs to Strasbourg in July.
Nigel Farage's new Brexit Party, which advocates leaving the EU without a formal agreement, came top of the European vote. But there was a strong showing from pro-EU parties, in particular, the Liberal Democrats, who want to reverse Brexit altogether.
Britain's two main parties — the Conservatives and the Labour opposition — were severely punished by voters. Many Conservatives are furious at the failure to “deliver Brexit”, while Labour has been accused of sitting on the fence.
The results indicated that opinion in the UK is becoming still more polarised over Brexit, confirming the results of surveys which suggest that people have become increasingly entrenched in two camps — those who wish to remain in the EU, and those who are determined to leave, even with no deal.
What did Theresa May's rejected Brexit divorce deal contain?
In November 2018 the British government and EU leaders approved a deal on the terms of the separation — the Withdrawal Agreement — and a Political Declaration on the nature of future EU-UK ties.
However, it was rejected three times by the UK parliament — leading to May's resignation as prime minister and her replacement by Boris Johnson.
His new deal struck with the EU replaces the Irish backstop, but maintains the provisions on the so-called divorce bill and on citizens' rights.
The legally-binding 600-page Withdrawal Agreement negotiated by the May government settles the key “divorce” issues: the UK’s financial obligations to the EU, citizens' rights — those of EU citizens living in the UK and Britons living on the continent — and arrangements for the Irish border. Set to become the only land frontier between the UK and the EU, both sides agree this must remain open, but the historically sensitive and complex issue bedevilled the talks.
A ratified exit deal would also pave the way for a the way for a planned transition period to come into effect after the UK’s departure. During this period many existing arrangements would remain in place, allowing for more time to sort out future EU-UK relations and avoid an abrupt “cliff-edge” exit.
If no UK-EU trade deal was agreed by the end of December 2020 — an extension to this period is possible — under May's deal the Irish backstop provisions would have come into play. These have been replaced by the new arrangements for Northern Ireland negotiated by Boris Johnson.
How has the Political Declaration changed?
The original 26-page Political Declaration also negotiated by the May government was much shorter and covers future relations. It is not legally binding but could form the basis for a trade agreement to be negotiated after Brexit.
Whereas Theresa May envisaged the UK remaining closely aligned to the EU, Boris Johnson wants to diverge and pursue a much more independent trade policy. His revised political declaration relates to a future EU-UK economic relationship where the UK opts for a Free Trade Agreement (FTA). But in return for zero tariffs and quotas, the UK makes "robust commitments on a level playing field" to ensure "open and fair competition".
Why did the UK parliament repeatedly reject May's deal?
At the heart of the debate over Europe in the United Kingdom is the balance to be struck between two objectives: a desire for independence, sovereignty and autonomy against the need to retain access to European markets, which, the EU has always insisted, means adhering to EU rules.
Theresa May insisted the negotiated withdrawal deal was in the national interest and there was no viable alternative. She argued that it delivered on the referendum result: an end to free movement, an end to huge UK payments to the EU, and an exit from the unpopular EU structures on farming and fishing.
However, the agreement brought hostility from both supporters and opponents of Brexit. In parliament, an alliance of forces resulted in the successive defeats for the government.
The main Labour opposition said the deal did not meet its six Brexit tests.
Derailed by the backstop
The controversial backstop, the mechanism in the agreement to guarantee an open border on the island of Ireland, proved to be a major stumbling block. The difficulty is that the frontier between Northern Ireland and the Republic of Ireland – one of the most politically sensitive borders in the world – will become an EU-UK land border after Brexit, yet the UK wishes to pursue an independent trade policy.
The backstop envisaged the UK remaining in a "single customs territory" with the EU in the absence of a free trade deal, as a kind of insurance policy to keep the border open.
Eurosceptic critics suspected it would have kept the UK strapped permanently to EU trade policy. EU sources pointed out that the UK-wide mechanism in the withdrawal agreement was included at the UK’s request, to avoid splitting off Northern Ireland from the rest of the UK.
Northern Ireland's Democratic Unionist Party (DUP), on whose support the May government depended, vehemently opposed any move it believes might separate Northern Ireland from the rest of the United Kingdom. Under the backstop, as set out in May's deal, Northern Ireland would stay aligned to some EU rules.
As the clock ticked down towards the original March 29 deadline, the UK and the EU said they had agreed a revised Brexit deal following weeks of deadlocked talks between London and Brussels. The British parliament had voted to seek “alternative arrangements” for the backstop after the first parliamentary defeat.
EU27 leaders had refused to alter the text of the withdrawal agreement. But Theresa May said she had secured legally-binding changes over the backstop’s application. European Commission President Jean-Claude Juncker said “meaningful legal assurances” had been given — while warning that there would be "no third chance" to revise the deal again.
However, leading members of the Conservative anti-EU European Research Group (ERG) and the DUP rejected the new proposals, after consulting new legal opinion on the deal from the government's top lawyer. The deal suffered a second defeat on March 12.
The government decided the third vote in the House of Commons on March 29 would be only on the withdrawal deal, not on the declaration on future relations. This was partly to conform to a ruling by the Speaker who insisted on substantial changes from the previous vote. However, it still ended in defeat by 58 votes.
The parliamentary deadlock prompted moves by MPs from different parties to wrest control of the Brexit process and allow a series of "indicative votes" to explore alternative solutions to the government's deal. But there has been no majority for any particular solution, other than an opposition to no-deal.
How did Brexit get into such a mess?
The turmoil in the British domestic political scene has cut across party lines. Internal party divisions have affected both the UK government and opposition.
The ruling Conservative party has long been riven between Eurosceptic and Europhile factions. The main Labour opposition has seen tension between its largely pro-EU membership and a leadership more inclined to deliver Brexit. Both parties have been damaged by the issue.
In early 2019, the Tories in particular haemorrhaged support to the new hardline Brexit Party. Meanwhile, both Conservatives and Labour suffered defections of some MPs to a new pro-EU centrist party — since renamed "The Independent Group for Change" — for reasons that included their leaders' stances on Brexit.
Tory turmoil boils over
The defeated UK-EU exit deal represented a compromise. But the blurring of several of Theresa May's so-called "red lines" on the limits of EU power sparked fury within her divided Conservative Party. As negotiations with Brussels brought more UK concessions, a string of government resignations followed.
After the 2017 general election, which left the Tories severely weakened in parliament, hostility amid their own ranks to any moves towards a "softer" Brexit restricted May's room for manoeuvre. Eurosceptics including the DUP strongly opposed her Brexit plan and the subsequent agreement, with many calling for the UK to leave the EU with no deal. They argue the accord ties the UK too closely to EU rules, compromising independence perhaps far into the future.
Equally, several pro-EU MPs also opposed a deal which, in their view, would leave the UK worse off than it had been inside the bloc. Some joined calls from opposition parties for a second referendum to see whether the country had changed its mind on Brexit.
Pressure from Tory Europhiles obliged the prime minister to open the door to a Brexit delay. Although she had long resisted calls from the Labour opposition for the UK to remain in a customs union with the EU, she suddenly changed tack on April 2 — only for cross-party talks to collapse weeks later.
Theresa May's fate was sealed after she revealed a fourth plan for getting her thrice-rejected Brexit deal through parliament. She tweaked the legislative package and crucially opened the door to a possible confirmatory referendum — a move which angered many in her party and sparked another government resignation.
What is the stance of UK opposition parties?
The main opposition Labour Party opposes Boris Johnson's deal with the EU and has instructed its MPs to vote against it in parliament.
In recent months Labour has been criticised for an ambiguous Brexit policy, blamed for its poor performance at local and European elections in May.
Despite gradually moving towards backing a public vote to resolve the Brexit crisis, the leadership's reticence to support Remain has angered many among its large pro-EU membership.
Leader Jeremy Corbyn has won backing for his strategy at the party's annual conference. His stance is to try to win an election, renegotiate a new Brexit deal with the EU which would be put to a public vote against an option of Remain. But his commitment to neutrality on the choice itself — set out in an article in the Guardian — has been criticised.
It was the latest in a series of interventions on the issue. On July 28 leader Jeremy Corbyn said Labour would campaign for the UK to remain in the EU if Boris Johnson tried to implement a no-deal Brexit.
He followed this up with a letter to MPs on August 14, vowing to hold a no-confidence vote in Johnson's government, which if passed would be followed by a temporary government under his leadership. Brexit would be delayed and a general election held — with Labour campaigning for a second referendum, with an option to remain in the EU.
Labour set out its position after the June 2016 referendum, saying it respected the result. It defined its priorities as securing a customs union with the EU and access to its markets, as well as ensuring the protection of standards over the environment, and consumer and workers' rights.
The party later moved to back a new EU referendum under certain conditions. Its National Executive Committee agreed on April 30, 2019, to support Labour's alternative plan for Brexit, and back a public vote if it couldn't secure changes to the government's deal or a general election.
The issue has caused internal divisions. Corbyn had resisted another referendum, and many MPs in Brexit-supporting constituencies are also hostile. But he has come under intense pressure from the party membership, and some prominent frontbench figures who favour another public vote.
Following Labour's election defeats in May, Corbyn said the "only way out" of the Brexit crisis was either a general election or a referendum on a deal. Deputy leader Tom Watson called for another referendum regardless, and for Labour to campaign for the UK to remain in the EU.
On July 9 Labour tipped further in the direction of advocating a public vote — and backing EU membership. In a letter to party members, Corbyn called for a referendum on any Tory deal — or no deal — on Brexit, adding that Labour would campaign to remain in the EU. However, the letter did not spell out what Labour would do in power — bringing more accusations of ambiguity.
The pro-EU Liberal Democrats and the Independent Group for Change both oppose Brexit, and support a second referendum on the UK's EU membership. So do the Green Party, the Scottish National Party (SNP), and the Welsh party Plaid Cymru.
The Liberal Democrats have enjoyed a boost in opinion polls and performed well in the European elections. Newly-elected leader Jo Swinson, has vowed to do "whatever it takes to stop Brexit". At the party conference in September she pledged that a Liberal Democrat government would immediately revoke Article 50 — the formal Brexit trigger.
The Brexit Party advocates leaving the EU on World Trade Organisation (WTO) terms, negotiating new terms afterwards — a position condemned as unrealistic and potentially disastrous by many mainstream politicians, economists and businesses. Leader Nigel Farage accuses the UK's political class of betraying the result of the 2016 referendum, adding that his new party's mission is to "change politics for good".
The UK Independence Party (UKIP), which Farage once led and was obliterated at the European elections, also favours a no-deal Brexit and blocking a second referendum.
A history of UK-EU tension
Check out our series on the history of the United Kingdom's complicated relations with the European Union:
How does the European Union work?
The EU originally developed after World War Two, with the aim of promoting economic co-operation and trade between countries to stop them from going to war again. Its members' economies are now integrated around a single market allowing the free movement of goods, people, services and capital.
Nineteen of the 28 member states use a single currency, the euro. The EU has its own institutions and passes laws affecting many issues across the union.
It highlights the benefits of membership as securing peace, promoting freedom and prosperity as part of the single market, safeguarding food and environmental standards, consumer benefits, protecting human rights, and enhancing Europe's global power.
The European Council is led by its president and is made up of the national heads of state or government, as well as the president of the Commission. It sets the EU's overall political direction but has no law-making powers.
Read more: What does the European Council do?
The European Parliament is the EU's law-making body, is directly elected by EU citizens, and represents them.
Read more: What does the European Parliament do?
The European Commission promotes the EU's general interest. It is made up of Commissioners, one from each member state, nominated by national governments. It proposes and enforces laws and implements EU policies and its budget.
Read more: What does the European Commission do?