Theresa May is under pressure from loyalist Brexit deal, amid fears it could be "heavily" rejected.
The prime minister was urged to postpone the decisive vote next Tuesday, as about 90 Conservatives are expected to rebel,
It came as supportive MPs suggested that details surrounding the Northern Irish backstop are changed.
Meanwhile, Mrs. May and Labor Leader Jeremy Corbyn were dashed as ITV withdrew their offer to host a televised debate.
The countdown is ticking closer to Tuesday's "meaningful vote" on the Brexit deal, with MPs completing their third day in five to debate it,
But the laquer of wavering backbenchers coming out in Mrs. May's favor to rattle her supporters.
Sir Graham Brady, who chairs the 1922 influential committee of Tory MPs, said most people wanted to "see this process moving forward".
But he admitted: "I do not think there's any point in plowing ahead and losing the vote heavily."
So the DUP's Ian Paisley quipped that "nothing like concentrating the mind like a hanging", warning that "the gallows are being built".
He asked International Trade Secretary Liam Fox about reports that ministers were considering the vote, or if "the government [is] fixed on walking towards those gallows ".
Dr Fox insisted the Brexit deal offered a "balanced and reasonable approach".
He added: "Of course [the government] wants to look for ways to give reassurance. "
Sky News understands Ms. May has failed to come to terms with the vote.
A Sky source also said the vote could not be resolved.
In a bid to assuage Tory Brexiteers, loyalist MPs published a plan to decrease the chances of the UK falling into the backstop.
The backstop has been created in Northern Ireland as in Great Britain.
Led by Hugo Swire, the plan would give MPs the chance to vote to end the transition period at the end of 2022 – rather than falling into the backstop.
Asked by Sky News If Downing Street has had a hand in its drafting, one of the plan's backers said: "There are probably several cooks involved in the broth."
The amendment wants to be debated as part of six by the Commons on Tuesday morning.
Former foreign secretary Boris Johnson, who has ruled out voting for Mrs. May's deal, said it was "simply not possible".
He said that, under the terms of the withdrawal agreement, a joint committee would make that decision.
It was also rejected by Arlene Foster, leader of the Democratic Unionist Party, which is propping up Mrs. May's government.
"Domestic legislative tinkering will not cut it," she wrote on Twitter.
"The legally binding international withdrawal would remain fundamentally flawed as evidenced by the attorney general's legal advice. "