Theresa May's flagship Brexit legislation has once more been thrown into doubt, after a compromise designed to keep Tory backbenchers on board was branded "unacceptable" by leading rebels.
The Prime Minister saw off defeat on the EU Withdrawal Bill at the last minute on Tuesday by persuading rebels that she would offer concessions to address their concerns about being given a truly "meaningful vote" on the final Brexit deal.
But an amendment tabled by Brexit Secretary David Davis on Thursday gives MPs no chance to block a "no deal" EU withdrawal if agreement has not been reached with Brussels by January 21 next year.
Instead, MPs would be allowed to vote only on a "neutral" motion, confirming that they have considered a statement by a minister on the issue. And crucially, the statement would be unamendable.
Leading pro-EU Conservative Dominic Grieve told the Press Association: "It is unacceptable in my view. It is not in accordance with the normal procedures of the House of Commons and it totally negates the point of the amendment, which was to give MPs a say."
Mr Grieve indicated that the final text of the amendment tabled in the House of Lords at the last possible moment on Thursday had been changed from the wording which he believed had been agreed earlier in the day.
He told PA: "After what had been a very sensible negotiation, I thought we had an agreement, and at the last moment, part of the text was changed to make the final motion unamendable if there isn't a deal by the end of January 21.
"I think it is unacceptable because it seems to me to be contrary to what the whole intention was behind this whole amendment."
Mr Grieve previously tabled his own proposals, which would have allowed Parliament to dictate the next steps the Government should take if no deal was reached by the end of February. This was seen as a means for MPs to ensure that the UK did not crash out of the EU without a deal.
However, the Grieve amendment was not put to a vote on Tuesday, after would-be rebels accepted "personal assurances" from the PM that a compromise would be found.
Instead, the majority of the pro-EU Tories backed the Government in voting down a Lords amendment to give them the power to tell ministers to go back to Brussels and renegotiate.
Now Conservative peer Viscount Hailsham has re-tabled Mr Grieve's amendment in the House of Lords, setting the scene for a fresh Government defeat when the Bill returns to the Second Chamber on Monday.