Former prime ministers Boris Johnson and Liz Truss have said they are going to vote against Rishi Sunak’s new Brexit deal for Northern Ireland.
The Windsor Framework was agreed by Mr Sunak and European Commission President Ursula von der Leyen on 27 February to change the way the Northern Ireland Protocol operates.
A crunch vote on the key part of the legislation will take place on Wednesday afternoon, when MPs will decide whether they want to back the Stormont brake or not.
Mr Johnson said the proposed new arrangements would mean the “whole of the UK” was unable “properly to diverge and take advantage of Brexit”.
And Ms Truss is understood to believe the PM’s pact does not “satisfactorily resolve the issues thrown up by” the protocol and “almost fatally impinges” on the UK’s ability to diverge from EU rules and regulations.
A source close to her said: “After examining the detail of the Stormont brake and Windsor Framework, Liz has decided to vote against the statutory instrument this afternoon.”
Mr Johnson said: “The proposed arrangements would mean either that Northern Ireland remained captured by the EU legal order – and was increasingly divergent from the rest of the UK – or they would mean that the whole of the UK was unable properly to diverge and take advantage of Brexit.
“That is not acceptable. I will be voting against the proposed arrangements today.
“Instead, the best course of action is to proceed with the Northern Ireland Protocol Bill, and make sure that we take back control.”
Mr Johnson has previously expressed doubts about the framework, while conceding he made mistakes in signing his contentious protocol.
The mechanism was agreed by Mr Johnson as part of his “oven ready” Brexit deal to prevent a hardening of the land border on the island of Ireland – which all sides agreed was necessary to preserve peace.
But it led to trade barriers being created between Great Britain and NI, effectively creating a customs border down the Irish Sea – something the former prime minister promised would not happen.
As a result Mr Johnson sought to pass the Northern Ireland Protocol Bill – a controversial piece of legislation aimed at overriding parts of the UK’s Brexit withdrawal agreement with the EU.
The move soured relations with Brussels, who said it would breach international law, and Mr Sunak paused the bill while attempting to negotiate a new deal after taking office.
The Windsor Framework aims to reduce red tape on goods passing between Northern Ireland and the rest of the UK by implementing a green and red lane system, while addressing the so-called “democratic deficit” through the Stormont brake.
This mechanism would allow a minority of politicians in Belfast to formally flag concerns about the imposition of new EU laws in Northern Ireland – a move that could see the UK Government veto their introduction in the region.
This is the only aspect of the framework currently being put to MPs for a vote, with Downing Street saying it is the “most significant” part of the agreement.
‘Government avoiding scrutiny’
Conservative backbencher Peter Bone said he was “pretty miffed” about the approach as he signalled he could also rebel against the government.
He told Sky News: “We were promised a full debate on the Windsor Framework. If I get a question at PMQs I’m going to ask the prime minister what happened to our wider vote?
“So I’m really pretty miffed that the government is avoiding scrutiny on this and on the brake itself it seems to fail all the tests.
“If that is the case, I’m going to listen to the debate. I’m going to go meetings this morning, but if I had to vote at this moment in time, I should vote against.”
With Labour backing the Windsor Framework agreement Mr Sunak should win the Commons division comfortably, despite criticism from some hardline Tory Brexiteers.
On Tuesday a group of Eurosceptic Conservative MPs described the Stormont brake as “practically useless”, though they stopped short of saying they would vote against it.
But even if the government wins the vote, the prospect of powersharing is up in the air after the DUP said they wouldn’t support the legislation.
The party pulled out of the Northern Ireland Assembly early last year in protest at the protocol, and on Monday said Mr Sunak’s new deal didn’t address the “fundamental problems” it caused.