Jeremy Corbyn has thrown his weight behind a move to delay Brexit in order to avoid the “chaos of a no-deal” exit.
MPs are expected to be given a chance to vote on an amendment to Theresa May’s Brexit deal on Tuesday, tabled by Labour’s Yvette Cooper and Tory Nick Boles.
If passed, MPs would then be able to vote for a Bill that would hand control of the Brexit process to parliament if the the prime minister fails to secure a deal by February 26.
MPs would get a vote on extending Article 50 to the end of the year and preventing a no-deal exit.
The support of the Labour frontbench increases the chances that the government will be defeated and the amendment will pass.
A Labour source said the party was backing the move, but would seek to shorten the possible extension of Article 50 proposed by Cooper and Boles.
“We’re backing the Cooper amendment to reduce the threat of the chaos of a no-deal exit,” the source said.
Keir Starmer, the shadow Brexit secretary, said the party was helping parliament “fill the void” left by the prime minister.
It comes as Boris Johnson said he is ready to back a compromise plan to salvage May’s agreement.
But the former foreign secretary said his support was dependent on the PM making clear she will demand legally-binding commitments on the controversial Irish “backstop” in the text of her Withdrawal Agreement.
Brussels has been adamant that it will not reopen the agreement, struck by May and European Commission president Jean-Claude Juncker and signed off by leaders of the remaining 27 EU states last November.
As MPs prepared for a crucial series of Commons votes which could shape the next phase of talks with the EU, international trade secretary Liam Fox indicated May was ready to reopen the agreement in order to secure a legally-binding text.
He urged Tory MPs to give her a “strong mandate” by backing an amendment tabled by 1922 Committee chairman Sir Graham Brady, which would replace the backstop with “alternative arrangements” to keep the Irish border open after Brexit.
Conservative MPs were informed on Monday evening that they would be whipped to vote for the amendment – assuming it is selected by Commons Speaker John Bercow.
Dr Fox gave a cool reception to a compromise deal put forward by housing minister Kit Malthouse which has won the support of the Democratic Unionist Party.
Drawn up by MPs from the Remain and Leave wings of the party co-ordinated by Malthouse, the compromise recasts the backstop as “free trade agreement-lite”, with a commitment on all sides there should be no hard border in Ireland and an extended transition period to December 2021.
DUP leader Arlene Foster – whose 10 MPs prop up the minority Conservative administration in the Commons – said the plan provided a “feasible” alternative to the backstop.