Raab said he could not “reconcile the terms of the proposed deal” [Henry Nicholls/Reuters]

Dominic Raab has resigned as UK’s Brexit Secretary over the proposed EU withdrawal agreement in a huge blow to British Prime Minister Theresa May.

“I regret to say that, following the Cabinet meeting yesterday on the Brexit deal, I must resign,” Raab said on Thursday. May’s plan threatened the integrity of the United Kingdom, he said.

“I cannot reconcile the terms of the proposed deal with the promises we made to the country in our manifesto at the last election. This is, at its heart, a matter of public trust,” he said in his resignation letter, published on his Twitter account.

European Union leaders will meet on November 25 to endorse the divorce deal that has been stalled over lack of consensus.

May will set out the terms of the draft withdrawal agreement on Thursday to the House of Commons, which must approve the deal before the UK leaves the European Union on March 29.

The PM secured the backing of her cabinet for the draft agreement on Wednesday, after a five-hour meeting.

“The collective decision of the government was that the cabinet should agree to the draft agreement and the outlying political declaration,” May said on Wednesday.

“This is a decisive step, which allows us to move on and finalise the deal in the days ahead,” she added. “These decisions were not taken lightly, but I firmly believe they were in the national interest.”

The main opposition Labour Party has also criticised the draft deal, saying it “breaches the prime minister’s own red lines”.

“This government spent two years negotiating a bad deal that will leave the country in an indefinite half-way house,” Jeremy Corbyn, the Labour Party leader, said.