Johnson tore down May's Chequers proposals during a speech on the sidelines of the Conservative party conference in Birmingham, which rekindled rumours that he may be gearing up for a leadership contest.
Here are the main takeaways.
'Chequers is a cheat'
Johnson called on the British government to scrap Chequers proposals unveiled in July by Theresa May, which offered a much softer vision of what the country's exit from the EU would look like than initially laid-out.
"If we cheat the electorate — and Chequers is a cheat — we will escalate the sense of mistrust," he said.
"We will give credence to those who cry betrayal, and I am afraid, we will make it more likely that the ultimate beneficiary of the deal will be the far right in the form of Ukip (United Kingdom Independence Party)," he added.
Under the Chequers plan — secured after months of public, political infighting within the British cabinet —the UK would maintain a common rulebook for all goods with the EU by committing to continued harmonisation with E rules.
It also offered concessions on the role of the European Court of Justice in UK-EU arbitration and proposed facilitated customs arrangement through which the UK could collect tariffs for the EU in order to avoid a hard border in Northern Ireland — one of the thorniest issues of the country's divorce with the EU.
But for Johnson — who resigned from his cabinet role to protest the Chequers plan — this "half-in, half-out" solution would not only be "undemocratic" but also show that "the United Kingdom, for all its power and might and network of influences around the world, for all its venerable parliamentary history, was ultimately unable to take back control."
Good Brexit deal 'in the interests' of the EU
The EU's goal in the Brexit negotiations is to constrain the UK, according to Johnson, who argued the EU would benefit from increased competition with the UK.
"In so many growth areas of the economy this country is already light years ahead: Tech, data, bioscience, financial services, you name it. We can use our regulatory freedom to intensify those advantages," Johnson said.
"And of course our European friends know that is possible — and that is exactly why they want to constrain us. Yet I would argue that it is actually in their interests too, to have the fifth biggest economy in the world, on their doorstep, acting as a continuing brake and caution to the over-regulatory instincts that have held the EU back for so long," he added.
The EU is bluffing
Johnson dismissed the EU's tough rhetoric as a bluff, arguing the bloc is acting tough to prevent other members from following in the UK's footsteps by exiting the union.
"Do not be fooled by the suggestion that the EU will ultimately reject these proposals," he asserted.
"Because what they want above all is to demonstrate above all – to any other country that might even dream of following suit – that you cannot leave the EU without suffering adverse political or economic consequences," he argued.
'There is time' for a deal
With just six months to go until the UK formally leaves the European Union and despite a deadline to reach a Withdrawal Agreement having already been pushed back to October, Johnson rubbished claims that time was running out to strike a new deal.
"Do not believe, then, when they say there is no other plan, no alternative," he told the packed auditorium.
He emphasised that a "super-Canada trade deal" — based on the 2016 EU-Canada trade agreement which removed 99% of customs duties on goods between the two sides — was possible, as championed by some in London.
But he also called on the UK to step up its preparations for a no-deal scenario which would see trade with the EU revert to World Trade Organization (WTO) rules.
"So now, therefore, is the time to truly take back control and follow that vision -- make it elegant, dignified, and graceful exit the country voted for.
"This is the moment — and there is time — to chuck Chequers, to scrap the Commission's constitutionally abominable Northern Ireland backstop, to use the otherwise redundant and miserable "implementation period" to the end of 2020 to negotiate the super-Canada FTA, to invest in all the customs procedures that we will need to ensure continued frictionless trade and to prepare much more vigorously for a WTO deal," he added.
Chequers would lead to second referendum
With negotiations appearing stalled, calls for a second referendum have been growing in the UK. During its own conference last week, Britain's main opposition Labour party overwhelmingly voted a policy to back another vote if no Brexit deal is reached.
For Johnson, May's Chequers plan not only raises the probability of a second referendum but the vote itself would be "disastrous"
"If Chequers is agreed, then it will only embolden those who are now calling for a second referendum," he said.
"There are the same people, incidentally, who explicitly told the electorate that there was no going back, that voting leave meant leaving the customs union and the single market, and that there was no way they would be asked again.
"They are now cynically campaigning to do just that, in a way that would be disastrous for trust in politics. People would see that they would simply be asked to vote again until they give the right answer the Remainers want.
"So the idea of a second vote is infamous — but the obvious democratic fragility of Chequers will only intensify such calls," he said.
'Back Theresa May's original plan'
Despite dismissing most of her proposals for an orderly Brexit, Johnson steered clear of outrightly attacking May and instead called for people to back her original, much tougher, plan for Brexit and her pledge that "no deal is better than a bad deal."
"I hope you will join me in urging our friends in government to deliver what the people voted for, to back Theresa May in the best way possible, by softly, quietly, and sensibly supporting her original plan. And in so doing it shows confidence in conservatism and it shows confidence in our country," he said.
"Because if we get it wrong, we will be punished. And if we get it right we can have a glorious future.
"This government will then be remembered for having done something brave and right and remarkable and in accordance with the wishes of the people," Johnson said.