A junior British justice minister said on Tuesday he will resign and will vote with pro-European Union rebels who want parliament to have the power to force the government to go back to the negotiating table if they reject a Brexit deal.
Details of precisely what this will involve will be agreed in the coming days when the bill is due to return to the House of Lords and ministers could table a fresh amendment.
"It was so positive it enabled quite a large number of my colleagues to vote to remove the Lords' amendments and substitute the Government's amendments".
After the resignation of justice minister Phillip Lee, who said he could not support the government's position on Brexit, it was said government whips feared a Tory rebellion on the "meaningful vote" amendment passed by the House of Lords.
The Prime Minister met pro-EU Tories in her private room in the Commons moments before the crucial vote to hear their demands for a truly meaningful vote on the final deal. Sources have said the government is happy to implement the first two points and will discuss the last one.
"In all conscience, I can not support the Government's decision to oppose this amendment because doing so breaches such fundamental principles of human rights and Parliamentary sovereignty. And I can not bring myself to vote for it in the bastion of liberty, freedom and human rights that is our Parliament".
Lee said "the people, economy and culture of my constituency will be affected negatively" by Britain's European Union departure, and it is "irresponsible to proceed as we are".
He said: "I'm conscious that if we're to make progress we ought to try and do this by consensus, but he must also understand the difficulty the House is in when it is faced with this kind of choice".
Opening the debate, Brexit Secretary David Davis insisted the government would abide by three principles to defend the will of the British people.
He said giving Parliament power to direct the government's hand in talks would be "an unconstitutional shift which risks undermining our negotiations with the European Union".
MPs voted 324 to 298 to reject the proposal, which had come to parliament after the Lords brought amendments to the EU (Withdrawal) Bill.
"We are asking members of parliament to abide by the referendum result, our manifesto commitment and to back our country", Andrew Bridgen, Conservative lawmaker and Brexit campaigner, told Reuters.
Solicitor General Robert Buckland intervened four times during a speech by the former Attorney General Dominic Grieve, whose amendment would effectively give MPs a veto on the government's negotiating agenda if a deal isn't done by the end of November. "We have no doubt of what was going on".
A dispute quickly arose about the third clause of Grieve's amendment, with Brexiters, including some ministers, quickly saying all that had been agreed was talks - and no government could agree to be "directed" by MPs. If she fails to deliver on her promises, she will lose their goodwill and face a backlash she won't be able to contain, people familiar with the matter said.
"Grieve's amendment puts that right and in a way Govt could and should accept it". The two sides aren't yet clear exactly on the terms of their deal, but it looks likely that Parliament will emerge with a greater say in the process.
He also warned any attempt by so-called hard Brexiteers to "overthrow" Mrs May would be "completely mad".
Just hours earlier, Downing Street had signalled the prime minister had no intention of accepting Grieve's compromise amendment to the European Union withdrawal bill, tabled by the former attorney general and aimed at ensuring ministers can't "crash out of the European Union by ministerial fiat", as he called it.