THE Brexit stakes have been dramatically raised after Jeremy Corbyn swung Labour behind a People’s Vote and Theresa May faced down some of her own colleagues by refusing to back a move to delay exit day beyond March 29.

As the febrile atmosphere at Westminster intensified ahead of tomorrow’s Commons vote, the Prime Minister returned to Britain from her attendance at the EU-Arab summit in Sharm el-Sheikh as the Labour leader was addressing a packed private meeting of the parliamentary party in the Commons.

During the two-hour conclave, passionate contributions could be heard from outside the Gladstone Room as journalists waited in the committee corridor.

Mr Corbyn told MPs: "The Prime Minister is recklessly running down the clock in an attempt to force MPs to choose between her botched deal and a disastrous no-deal. We cannot and will not accept that.”

He said Labour's alternative Brexit plan - contained in an amendment - for a comprehensive customs union with a UK say, close alignment with the single market and guarantees on rights and standards was “serious and credible”.

The party leader made clear Labour would also be backing the amendment, proposed by his colleague Yvette Cooper, to extend the Article 50 process in a bid to rule out a no-deal outcome.

“One way or another, we will do everything in our power to prevent no-deal and oppose a damaging Tory Brexit based on Theresa May's overwhelmingly rejected deal,” declared Mr Corbyn.

Then he added: "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."

At first there was a deal of confusion as to whether an option to Remain would be on the ballot paper of a Labour-supported People’s Vote. Some Remainer MPs emerged unsure as they said Mr Corbyn had not been specific about the Remain option in his answers.

But others insisted the position was clear. One peer said Remain would “inevitably” be on the ballot paper, stressing: “Otherwise what would be the point? You can’t have a People’s Vote with one question.”

Backbencher Owen Smith, who challenged for the leadership in 2016, said: “This was always the right policy for Labour. This is where we should have been at the beginning.”

His Labour colleague Ian Murray, a leading Remainer, described the leadership’s position as “unequivocal,” adding: “This is significant progress and now we must win the arguments to get a majority in Parliament to win a public vote with the option to remain.”

But some MPs were unhappy. Lucy Powell, who represents Manchester Central, estimated some 25 colleagues would vote against a second referendum.

John Mann, the Nottinghamshire MP, claimed people in the North of England would "never vote Labour again". He told Mr Corbyn: “This decision will stop you being Prime Minister.”

Meanwhile, Brandon Lewis, the Conservative Chairman, accused the Labour leadership of having “ripped up their promise to respect the referendum result”.

He added: “Jeremy Corbyn's Labour want to betray the will of the British people and ignore the biggest democratic vote in our nation's history.”

It is thought part of the Labour leadership’s calculation was to try to stem the defections to the centrist pro-Remain Independent Group, which has seen eight MPs leave Labour to join it.

Today, the Government is expected to table the motion for debate tomorrow. While some MPs have suggested Mrs May might try to kill off support for the Cooper amendment by signalling she would not allow the country to crash out of the EU without a deal, she was adamant in Sharm el-Sheikh that she would not support extending Article 50.

The PM told a press conference: “A delay in this process does not deliver a decision in Parliament, it doesn’t deliver a deal; what it does is precisely what the word says.”

After a raft of meetings on the sidelines, which included talks with Germany’s Angela Merkel, Ireland’s Leo Varadkar and the European Commission President Jean-Claude Juncker, Mrs May told journalists: “I have a real sense from the meetings I have had here, conversations I have had with EU leaders in recent days…we can achieve that deal. It’s within our grasp to leave with a deal on March 29 and that’s where all our energies are going to be focused.”

The PM, who has put off having a meaningful vote this week but promised one by March 12, admitted there was “still more work to do”.

But she noted: “What I have sensed in all of my conversations with my fellow leaders both here in Sharm el-Sheikh and in recent days is a real determination to find a way through, which allows the UK to leave the EU in a smooth and orderly way with a deal.”