The Government faces another battle to appease Brexit rebels in the Commons after Lords again backed giving MPs a "meaningful vote" on the final Brexit deal.
The to-and-fro over Parliament's role as the UK leaves the EU will return to the Commons after peers inflicted another heavy defeat on the Government on Monday.
They backed an amendment to the EU (Withdrawal) Bill, tabled by Viscount Hailsham, which would require the Government to allow MPs to vote on how it would proceed in the absence of a Brexit deal by January 21 next year.
MPs will now vote on whether to adopt the motion, which was brought in after pro-EU rebels led by former attorney general Dominic Grieve accused the Government of reneging on measures they believed had been agreed to stave off a rebellion last week.
Prime Minister Theresa May had earlier on Monday warned against any moves to "tie her hands" during negotiations with Brussels, saying that Parliament must not be able to "overturn the will of the British people".
The Prime Minister said she had been listening to the concerns of critics but the legislation must not restrict her freedom in talks with Brussels.
"As we keep faith with people who voted to leave the European Union, and many of those who didn't but are now saying 'let's just get on with it', we need to make sure we are putting this legislation into place," she said.
"But as we do that, of course we have been listening to concerns about the role of Parliament, but we need to make sure that Parliament can't tie the Government's hands in negotiation and can't overturn the will of the British people."
Under Government plans, if MPs reject the agreement reached by Mrs May with Brussels, or if no deal has been obtained by January 21, Parliament will be offered the opportunity to vote on a "neutral motion" stating it has considered a minister's statement on the issue.
Crucially, the motion will be unamendable, meaning MPs cannot insert a requirement for Mrs May to go back to the negotiating table, extend the Brexit transition or revoke the UK's withdrawal under Article 50.
The Hailsham amendment, dubbed "Grieve 2" by the peer, was tabled after Mr Grieve warned that the Tory rebels he leads could "collapse" the Government if they disagree with the final outcome of withdrawal talks, and had the right to a proper say on Brexit.
Mr Grieve insisted rebels would only accept a "meaningful vote" and not the "slavery clause" the Government was offering.
The Department for Exiting the EU (DExEU) said that it "cannot accept" the amendment which was passed by a majority of 119 and would seek to overturn it when it returns to the Commons on Wednesday.
A DExEU spokesman said: "Agreeing to amendable motions would allow Parliament to direct Government on its approach to exiting the EU and so does not meet the reasonable tests set out by the Prime Minister and Brexit Secretary last week."
Leading backbencher Brexiteer Jacob Rees-Mogg said that the meaningful vote was being used to "obstruct Brexit" and "thwart the referendum result".
He accused the House of Lords of being "cavalier" and acting against its own long-term interests, adding: "An unamendable motion is parliamentary accountability. An amendable motion could be used to stop Brexit."
Lord Hailsham said that Mr Grieve, who watched the Brexit Bill debate at the bar of the Lords, believed he had made an agreement with the Solicitor General last week but it appeared "senior ministers" had objected to it and it had now been "repudiated".
The peer said he was asking the Lords to allow MPs to vote on what Mr Grieve believed was agreed with the Government.
He added: "The Government's amendment not only fails to deliver the promised meaningful vote.
"That would be an act of omission and bad enough.
"But this is far worse.
"The Government is seeking to make the promised meaningful vote impossible and that is an act of commission contrary to what ministers have promised."
Shadow Brexit minister Matthew Pennycook said: "If the Prime Minister's final Brexit deal is voted down that cannot give her licence to crash the UK out of the EU without an agreement.
"MPs now face a decisive vote on Wednesday to guarantee Parliament has a proper role in the Brexit negotiations and to take the threat of no deal off the table once and for all."