In the most significant step towards a new vote on Brexit, the Labour leader said he was committed to “putting forward or supporting an amendment in favour of a public vote to prevent a damaging Tory Brexit being forced on the country”.
However, a second EU referendum still face a significant hurdles, with a People’s Vote still unable to command majority support in the Commons.
The announcement comes with Downing Street braced for resignations today by Remain-supporting ministers left unmoved by Theresa May’s promise of a vote on her Brexit agreement by 12 March, just 17 days before the UK could crash out of the EU without a deal.
One senior government insider said Number 10 was “very worried” about ministers walking out over the failure to accept a delay to Brexit in order to rule out a no-deal.
“If there aren’t any resignations by ministers or PPSs [Personal Parliamentary Secretaries] today, we’ll be very surprised,” the source said.
At a press conference in Egypt on the margins of an EU-Arab summit, Mrs May said she was sticking to her timetable to deliver Brexit on 29 March.
“It’s within our grasp to leave with a deal on March 29 and that’s where all of my energies are going to be focused,” she said.
“An extension to Article 50, a delay in this process, doesn’t deliver a decision in Parliament, it doesn’t deliver a deal. All it does is precisely what the word ‘delay’ says.”
Asked if MPs might be asked to vote on additional assurances over the controversial Irish border backstop on 12 March, before they have been formally signed off by EU leaders at a summit a week later, the Prime Minister told reporters: “It is possible to do it either way.”
European Council president Donald Tusk revealed he discussed legal details of extending the Article 50 withdrawal process in talks with Mrs May when they met on Sunday in Egypt.
Mr Tusk said delaying the UK’s withdrawal is now a “rational solution”, warning that the only alternative if MPs cannot agree a deal is “a chaotic Brexit”.
And Dutch Prime Minister Mark Rutte, who had talks with Mrs May in the Red Sea resort of Sharm El-Sheikh on Monday, said the UK needed to “wake up”.
Mr Rutte said: “We are sleepwalking into a no-deal scenario. It’s unacceptable and your best friends have to warn you.
“Wake up. This is real. Come to a conclusion and close the deal.”
In a furious Brexit diplomatic effort on the fringes of a summit focused on Middle East cooperation, Mrs May also met with European Commission president Jean-Claude Juncker, German Chancellor Angela Merkel, Irish Taoiseach Leo Varadkar and Italy’s Giuseppe Conte.
The Prime Minister confirmed that Brexit negotiators will return to Brussels on Tuesday for further talks with EU chief negotiator Michel Barnier.
She will make a statement to the Commons this afternoon ahead of votes on Brexit tomorrow, knowing that senior cabinet ministers and up to 100 of her MPs could rebel to back amendments ruling out a no-deal scenario.
At the weekend, Work and Pensions Secretary Amber Rudd, Business Secretary Greg Clark, and Justice Secretary David Gauke threatened to back an amendment put forward by Labour MP Yvette Cooper and Tory Oliver Letwin, which seeks to block a no-deal through legislation if there no Brexit agreement in place by 13 March - a day after Mrs May’s deadline for a ‘meaningful vote’.
The government source said any ministers who backed the amendment “will be expected to resign”.
With the threat of further resignations by and the party losing support in the polls, Mr Corbyn told a meeting of his parliamentarians that Labour would “do everything in our power to prevent No Deal and oppose a damaging Tory Brexit based on Theresa May’s overwhelmingly rejected deal.
“That’s why, in line with our conference policy, we are committed to also putting forward or supporting an amendment in favour of a public vote to prevent a damaging Tory Brexit being forced on the country.”
Labour is in talks with backbench MPs Peter Kyle and Phil Wilson over an amendment they are proposing that would approve Mrs May’s deal, but put it to a public vote. The Labour leadership would rather voters be presented with a choice between its own deal and remaining in the EU, as it tries to strike a balance between pro- and anti-Brexit opinion amongst its supporters.
The Kyle-Wilson amendment is not expected to be tabled tomorrow, but could be pushed forward on the day of the meaningful vote in March.
Last night the shadow Foreign Secretary Emily Thornberry said Labour would seek a “deal or remain” referendum.
Politicians and campaigners backing a People’s Vote issued a cautious welcome to the announcement. Edinburgh MP Ian Murray, one of its strongest advocates, said the announcement was “significant progress”, but said campaigners had to “win the arguments to get a majority in Parliament to win a public vote with the option to remain”.
First Minister Nicola Sturgeon said: “A referendum with no remain option would be ludicrous”.