Both Boris Johnson and Liz Truss will vote against Rishi Sunak’s Brexit deal in Parliament.

Mr Johnson confirmed on Wednesday that he will not be backing the deal when MPs vote on the Stormont brake in the Commons later on Wednesday, with Ms Truss set to follow suit.

In a statement, 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.”

A source close to Ms Truss said that she plans to vote against it too.

Ms Truss is understood to believe the Prime Minister’s Windsor pact does not “satisfactorily resolve the issues thrown up by” the Northern Ireland Protocol and “almost fatally impinges” on the UK’s ability to diverge from EU rules and regulations.

With Labour backing the Windsor Framework agreement signed last month, the Government should win the Commons division comfortably, despite criticism from some hardline Tory Brexiteers.

The DUP has already said its eight MPs will vote against the regulation to implement the Stormont brake as it continues to seek changes to the overall framework.