Boris Johnson has appealed to MPs to get behind his Brexit deal, warning any further delay would be “pointless” and “corrosive” of public trust.
With Parliament sitting on Saturday for the first time in 37 years, the Prime Minister said the agreement he struck in Brussels represented “the best possible solution”.
However he faces the prospect of further deadlock in the Commons, with opposition parties threatening to withhold approval until legislation to implement the deal is in place.
The architect of the plan, former cabinet minister Sir Oliver Letwin, said it was simply an “insurance policy” to ensure the UK could not “crash out” of the EU without a deal on October 31.
With many of his fellow MPs who had the Tory whip withdrawn expected to back the amendment, the Government is facing a strong possibility of defeat.
If they lose, it is expected that ministers will simply order Conservative MPs to go home without voting on the main motion to back the deal.
They are then expected to introduce the legislation to implement the agreement next week in bid to get it through Parliament by the deadline of October 31.
A Government source said: “A vote for Letwin is a vote for delay.
“The public would be appalled if MPs just vote for another pointless delay again.”
Labour, however, confirmed that it would be supporting the amendment.
If it is passed, supporters argue that the so-called Benn Act will come into play, requiring Mr Johnson to write to Brussels seeking a further delay to Britain’s withdrawal.
In his opening statement, the Prime Minister urged MPs to abandon the “delusion” that they could simply delay Brexit yet again.
“Whatever letters they may seek to force the Government to write, it cannot change my judgment that further delay is pointless, expensive and deeply corrosive of public trust,” he said.
“And people simply will not understand how politicians can say with one breath that they want delay to avoid no deal and then with the next breath that they still want delay when a great deal is there to be done.
“Now is the time to get this thing done, and I say to all members let us come together as democrats to end this debilitating feud.”
With Mr Johnson’s erstwhile allies in the DUP fiercely opposed to the proposed customs arrangements for Northern Ireland, the vote is likely to be close.
The Prime Minister insisted that his plan would meet the “special circumstances” in Northern Ireland and the need to maintain an open border with the Republic.
But DUP deputy leader Nigel Dodds called on him to honour his commitment to deliver Brexit for “the whole of the United Kingdom”.
“Weariness in this House over Brexit should not be an excuse for weakness on Brexit or weakness on the Union,” he said.
With every vote potentially crucial, Mr Johnson sought to reach out to Labour MPs who have indicated they could back a deal, insisting he was committed to the “highest standards” of workers’ rights and environmental protections outside the EU.
However he was accused by Jeremy Corbyn of making “empty promises” saying he had spent weeks secretly negotiating to have legally binding commitments in Theresa May’s Brexit deal removed.
“This Government cannot be trusted and these benches will not be duped,” the Labour leader said.
“Voting for a deal today won’t end Brexit. It won’t deliver certainty and the people should have the final say.
“Labour is not prepared to sell-out the communities we represent. We are not prepared to sell out their future. And we will not back this sell-out deal.”