A junior Wales Office minister has quit over the prime minister’s decision to turn to Jeremy Corbyn to try to get a Brexit deal through Parliament.
Nigel Adams said the decision was a “grave error” and the UK would now “end up in a customs union” with the EU.
Mr Adams, who was also a government whip, said he believed the UK would have coped with a “managed no-deal”.
He became the fourth Wales Office minister to be appointed in a year when he took up the role last November.
Theresa May is to meet Mr Corbyn later see if they can formulate a deal that both sides in Parliament can agree to.
She said if it was not possible to agree, they could choose a series of options to put to the House of Commons.
In his resignation letter, Mr Adams tells Mrs May: “I and many others agreed with your previous position that no deal was better than a good deal.
“It now seems that you and your cabinet have decided that a deal – cooked up with a Marxist who has never once in his political life put British interest first – is better than no deal.”
Welsh Secretary Alun Cairns said he was “disappointed to see Nigel leave government and would like to thank him for all his work and efforts as a minister”.
“My department and I are committed to delivering on our priorities,” he said.
Tory MP for Montgomeryshire Glyn Davies said he was “really sorry to see Nigel leave the Wales Office”.
He’s a really good MP, and I will miss working with him,” he said.
But Labour Welsh assembly member Alun Davies, said it was the resignation “someone no one in Wales has ever heard of”.
“Another reason why the Wales Office should be abolished,” he tweeted.