The government secured a knife-edge victory by overturning a Lords bid to give MPs a “meaningful vote” and the power to prevent a no-deal Brexit during a dramatic day of votes on the EU (Withdrawal) Bill.
In a major climbdown, Robert Buckland, the solicitor general, told the Commons that ministers would consider key aspects of a compromise amendment by former attorney general Dominic Grieve, which opened the door to MPs taking control of the negotiations, if ministers fail to strike a deal in Brussels.
Rebels want that to happen if there is no deal by the end of November – but it is unclear whether Mr Buckland will agree to that date in a further amendment to be tabled in the House of Lords.
But it is the first time that Ms May appears to be considering the prospect of a deadline for success in the talks.
Negotiations went down to the wire as the prime minister reportedly summoned rebels to her Commons office to give them face-to-face assurances shortly before voting began.
The government’s chief whip Julian Smith could also be seen collaring potential rebels in the chamber during the debate in a frenzied attempt to head off a revolt.
Former chancellor, Ken Clarke, and Tory backbencher Anna Soubry both voted against the government but the revolt lost momentum as other pro-EU Tories such Sarah Wollaston and Antoinette Sandbach appeared to be satisfied by the concession.
Five Labour MPs rebelled by backing the government, including Brexiteers Ronnie Campbell, Frank Field and Kate Hoey.
Mr Grieve said he had backed the government after receiving assurances, telling Sky News: “I am quite satisfied we are going to get a meaningful vote.”
Fellow Tory remainer Stephen Hammond told BBC Radio 4’s PM: “We have spoken in a room with the prime minister this afternoon, 10 minutes before the first round of voting.
“I absolutely trust what the prime minister says to us.”
Well-respected Conservative backbencher Sarah Wollaston also announced she would support the government as long as a promised further amendment in the Lords next week “closely reflects” the Grieve proposals.
Ms May appears to have escaped defeat for now, as a potential clash over the customs union on Wednesday appears to have been defused.
However there could be another bout of parliamentary ping pong with the Lords, where the bill goes back and forth between the two chambers.
Earlier, justice minister Philip Lee resigned from the government in order to back Mr Grieve’s amendment, in a blow to the prime minister’s authority.
“If, in the future, I am to look my children in the eye and honestly say that I did my best for them I cannot, in all good conscience, support how our country’s current exit from the EU looks set to be delivered,” said Dr Lee later told the Commons.
He later abstained on the crucial vote, saying he was “delighted” that ministers had agreed to introduce an amendment giving parliament “the voice I always wanted it to have in the Brexit process”.
Shadow Brexit secretary Sir Keir Starmer said: “Facing the prospect of a humiliating defeat, Theresa May has been forced to enter negotiations with her backbenchers and offer a so-called concession.
“We will wait and see the details of this concession and will hold ministers to account to ensure it lives up to the promises they have made to parliament.”
Liberal Democrat Brexit spokesman Tom Brake said: “At the 59th minute of the 11th hour, as has become a tradition in Brexit negotiations, the Tories have been forced to cobble together a compromise.
“Time will tell as to whether this is just another attempt to buy off the rebels or a real attempt at consensus. But if we face the prospect of a ‘meaningless process’ rather than a ‘meaningful vote’, parliament will be enraged.”
Ministers voted to overturn a string of Lords amendments, which sought to remove the official exit date from the bill and to hand more powers to parliament’s sifting committee to scrutinise secondary legislation.