UK Prime Minister Theresa May has vowed to fight on as anger over her Brexit deal threatens to spill over into a leadership contest.
Amid a wave of resignations from the heart of government on Thursday, May's fiercest critics began calling for a vote of no confidence in her.
Only a handful of Conservative MPs have so far admitted to doing so, but if at least 48 demand the vote then May could be deposed.
If her own MPs don't oust her first, May still has to get the EU divorce deal through a deeply- divided parliament.
She claimed on Wednesday evening that her cabinet of senior MPs had backed the agreement she brought back from Brussels.
But the unanimity of this approval began looking flimsy by Thursday morning when Dominic Raab, the UK's Brexit chief, quit the government.
"No democratic nation has ever signed up to be bound by such an extensive regime, imposed externally without any democratic control over the laws to be applied, nor the ability to decide to exit the arrangement," Raab said in his resignation letter.
Raab and work and pensions minister Esther McVey were the most prominent of seven people to quit the government.
After a grilling by MPs in the House of Commons, May emerged to face the looming prospect of a leadership challenge.
Key Brexiter Jacob Rees-Mogg stood outside parliament to announce he would write to the 1922 Committee to call for a vote of confidence in May.
When May then called an 18h CET press conference in Downing Street, some might have expected her to join the list of resignations.
But she came out fighting and referenced cricket legend Geoffrey Boycott as she vowed to show the perseverance to push her Brexit plan through.
"Am I going to see this through? Yes," May said. "I am going to my job of getting the best deal for Britain and I'm going to my job of getting a deal that is in the national interest."
She added: "I believe with every fibre of my being that the course I have set out is the right one for our country and all our people."
By seeking to preserve the closest possible ties with the EU, May has upset her party's many advocates of a clean break, and Northern Ireland's Democratic Unionist Party (DUP), which props up her minority government.
Meanwhile, proponents of closer relations with the EU in her own party and the Labour opposition say the deal squanders the advantages of membership for little gain.
Both sides say it effectively cedes power to the EU without securing the promised benefits of greater autonomy.
"It is ... mathematically impossible to get this deal through the House of Commons. The stark reality is that it was dead on arrival," said Conservative Brexit-supporting lawmaker Mark Francois.
May will need the backing of about 320 lawmakers in the 650-seat parliament to pass the deal.
The ultimate outcome remains uncertain. Scenarios include May's deal ultimately winning approval; May losing her job; Britain leaving the bloc with no agreement; or even another referendum.