MPs will today try to force Theresa May to return with a Brexit Plan B within just three days if, as expected, her current proposal is rejected next Tuesday.

In what is now a battle between Parliament and Government over Britain’s future, the Commons must approve a business motion before MPs this afternoon resume the debate, due to last five days, on the Prime Minister’s Plan.

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In a dramatic move this morning, the Commons Speaker, John Bercow, seemingly against the advice of the parliamentary clerks, has accepted an amendment to the business motion by a cross-party group of MPs, led by the former Conservative Attorney General Dominic Grieve. Whitehall sources had suggested the Government motion was "bomb-proof".

If the rebel motion passes, it will force Mrs May to return to the Commons “within three sitting days” to put forward her alternative. MPs intend this to be amendable, so that they could prevent a no-deal and, possibly, demand a People’s Vote.

Under current procedure, the PM has 28 days to come up with a Plan B but if the MPs’ amendment were passed, she would have to produce one by the end of next week.

Labour’s Chris Leslie said: “If and when the PM’s plan is voted down on Tuesday, MPs can’t be made to wait potentially until February 12 for the next vote. The situation is too urgent now.”

In other developments:

*Labour confirmed Jeremy Corbyn would table a motion of no confidence in the Government almost immediately if Mrs May lost the Brexit vote next week;

*Cabinet Office Minister David Lidington said the public was not served by “fantasies about magical alternative deals that are somehow going to sort of spring out of cupboard in Brussels”;

*Mr Lidington, the PM's de facto deputy, warned a no-deal would cause “months” of disruption to food and goods at border but a Calais port official insisted talk of delays was overblown. “Trucks will be passing as they do today,” he said and

*Chris Heaton-Harris, the Brexit Minister, said there was no "parliamentary route" that would allow pro-EU MPs to stop the UK leaving the EU.

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Last night, MPs opposed to a no-deal break flexed their muscles to inflict another bruising defeat on the Government.

Some 20 Conservative MPs joined opposition parties in backing a cross-party amendment to the Finance Bill intended to limit the Government's powers to make tax changes in the event of no-deal.

The rebels included former ministers Ken Clarke, Sir Michael Fallon, Justine Greening, Mr Grieve, Sir Oliver Letwin and Sam Gyimah.

Sir Oliver, who supports Mrs May’s Plan, said they were ready to table similar amendments to other Brexit legislation to warn they were prepared to put paid to a no-deal outcome, which, he said, was a “disastrous proposal".

"The majority in this House will sustain itself and we will not allow a no-deal exit to occur on March 29," he said.