The Foreign Secretary cemented his position as Brexiteers’ alternative leader in a Commons resignation statement that trashed Theresa May’s White Paper, saying it offered “Brexit in name only”.
Earlier, the Prime Minister was put on the spot by one of her MPs, who asked when it was she decided that “Brexit means Remain”.
Mrs May hit back at the claim, telling her critics she was trying to find a “workable” solution to issues with the EU.
But she was given a warning of the growing pressure she will face through the summer recess unless she abandons her Brexit policy, with Mr Johnson accusing the government of “dithering” and leading the country into a “fog of self-doubt”.
Mr Johnson did not issue a direct challenge to the Prime Minister’s position, but hinted at a possible leadership bid, telling MPs: “It is not too late to save Brexit.”
Jacob Rees-Mogg, the other leading figurehead of the Eurosceptic win of the Conservative Party, described it as “the speech of a statesman”.
In what appeared to be a deliberate bid to invoke history, the former Foreign Secretary gave his speech from the same position as Geoffrey Howe when he delivered his resignation statement in November 1990, hastening the end of Margaret Thatcher’s premiership.
In his 12-minute statement, he said: “It is not too late to save Brexit. We have time in these negotiations. We have changed tack once and we can change again.
“The problem is not that we have failed to make the case for a free trade agreement of the kind spelt out at Lancaster House.
“We haven’t even tried. We must try now because we will not get another chance to do it right.”
Dismissing concerns from Brussels and Dublin over the Irish border, Mr Johnson called on the Prime Minister to return to the “glorious” plans she set out in a speech at Lancaster House last year - “a strong, independent self-governing Britain that is genuinely open to the world, not the miserable permanent limbo of Chequers.”
He added: “That is the prize that is still attainable. There is time.
“If the Prime Minister can fix that vision once again before us, then I believe she can deliver a great Brexit for Britain with a positive, self-confident approach that will unite this party, unite this House and unite this country as well.”
Mr Johnson warned that under Mrs May’s proposals, the UK was “volunteering for economic vassalage”, and denounced her customs plan for the Irish border as a “fantastical Heath Robinson” creation.
He told the Prime Minister not to “make the fatal mistake of underestimating the intelligence of the public, saying one thing to the EU about what we are really doing and pretending another to the electorate”.
Earlier, at PMQs, Mrs May was caught blue-on-blue attacks between Tory MPs, with Brexit supporter Andrea Jenkyns asking: “Can the Prime Minister inform the House at what point it was decided that Brexit means Remain?”
The Prime Minister was backed by Brexiteer Tory MP David TC Davies, who said it was “high time that Labour MPs, and, yes, some Conservatives, stop the fear-mongering, get behind their country and support the Prime Minister as she leads us out of the European Union.”
And the MP Keith Simpson made Mr Johnson the butt of a joke, commending the Prime Minister “for her sangfroid a week ago in dealing with a giant ego—somebody who believes that truth is fake news and leaks continually” before pointing out he meant Donald Trump.
Labour leader Jeremy Corbyn claimed the government was “failing to negotiate Brexit, failing to meet the needs of the country because they are far too busy fighting each other”.
The SNP leader Ian Blackford told Mrs May she had “lost control of her own party” and was “is in office but not in power”.
Mr Blackford called for the Article 50 process, which sets out the UK’s exit date of 29 March 2019 in law, should be extended for at least six months to allow negotiations to reach a deal.