Rebel Conservatives are warning they could combine with Labour and the SNP to amend the Brexit Bill unless Parliament is given a say on the "endgame" negotiations.
Pro-Remain Tories fear Theresa May's warning she would prefer "no deal to a bad deal" could see Britain "falling off a cliff" if negotiations broke down.
Backbencher Neil Carmichael expressed concern that, as it stood, MPs would be unable to force the Prime Minister back to the negotiating table, with potentially disastrous consequences for the economy.
Writing in The Mail on Sunday, he warned that he was not the only Tory MP to feel strongly about the issue.
"I hope to persuade the Government to meet our concerns this week before the Brexit Bill is finalised," he said.
His intervention came as ministers prepared to take the EU (Notification Of Withdrawal) Bill back to the Commons for its committee stage, with three more days of debate starting on Monday.
It will be a chance for MPs to amend the legislation - which gives ministers the power to trigger Article 50 marking the start of formal withdrawal process - after last week's second reading vote on the principle of the Bill.
The Government has sought to restrict the opportunities for change by limiting it to just two clauses. Speaker John Bercow will decide on Monday which of the scores of amendments MPs will have a chance to vote on.
The prospect of a Government defeat has infuriated pro-Brexit Conservatives who accused the Tory rebels of trying to derail the Bill.
Leading Tory Leave campaigner Steve Baker claimed there are as many as 27 Conservative MPs who could vote with Labour and the SNP.
"This is a time to unite behind a democratic result not plot to repudiate it. Any vote to amend this simple Bill is a vote against implementation of the referendum result," he said.
That figure was dismissed as being far too high by the pro-Remain camp, but with a Government majority of just 16 in the Commons, the voting arithmetic may be tight.
Former ministers Anna Soubry and Dominic Grieve were among those reported to be considering voting for an amendment alongside the veteran pro-European Ken Clarke who was the lone Tory to rebel at second reading.
In his article, Mr Carmichael said that in his view, Parliament had to have a final say when they reached "the endgame" in the negotiations.
"We could be faced with the prospect of leaving the EU by 'falling off a cliff' - as some have described leaving with no deal - with potentially disastrous economic consequences," he said.
"But MPs would have no chance to say the Government should step back from the brink and return to the negotiating table.
"To argue that MPs can have a say if we achieve a deal, with all the safeguards implied by it, but no say if we walk away with none of these, defies logic.
"If that occurred, it would be even more important for MPs to be able to vote for or against it."