Former Justice and Housing minister Raab, who replaced David Davis in July, announced in a tweet that he had resigned from the Cabinet, although he paid tribute to the Prime Minister.
Mr Raab, who backed Brexit in the 2016 referendum, posted: “Today, I have resigned as Brexit Secretary. I cannot in good conscience support the terms proposed for our deal with the EU. Here is my letter to the PM explaining my reasons, and my enduring respect for her.”
Esther McVey announced her resignation around an hour later.
In the letter, Mr Raab says that he cannot support the deal due to the proposed agreement’s proposals on Northern Ireland, which he argues is a ‘very real threat to the integrity of the United Kingdom.”
He goes on to criticise the ‘indefinite backstop’ arrangement, which he argues amounts to a form of veto held by the EU over the terms of Britain’s departure.
The Esher and Walton MP concludes: “Above all, I cannot reconcile the terms of the proposed deal with the promises we made to the country in our manifesto at the last election.”
Mr Raab and Ms McVey’s resignations were the first signs of cabinet-level revolt against Mrs May, although junior Northern Ireland Minister Shailesh Vara quit earlier this morning.
SNP Westminster leader Ian Blackford said the resignations were a fatal blow to Theresa May’s leadership.
“With ministers falling like dominos, it’s clear the Prime Minister lacks the confidence of her cabinet – and has no hope of commanding a majority in parliament for her bad Brexit deal.
“Dominic Raab is the second Brexit Secretary to resign in just four months.
“The Tory government is now consumed by chaos and lacks any authority whatsoever.”