Brexit Secretary Stephen Barclay, right, and attorney general Geoffrey Cox have failed to make a breakthrough in their EU negotiations Jack Taylor/Getty Images

Talks to save Theresa May’s Brexit deal stalled last night after European Union negotiators refused to give Geoffrey Cox, the attorney general, “reasonable” assurances on the Irish backstop.

Three and half hours of talks in Brussels between Michel Barnier, the EU’s lead negotiator, Mr Cox and Stephen Barclay, the Brexit secretary, ended in a bad-tempered stalemate.

Negotiations will now go to the wire this Friday, running into the weekend, to try to find guarantees that will enable Mr Cox to change his legal advice on the Irish backstop before the crucial Brexit vote in the House of Commons next Tuesday.

“There are very sensitive discussions. We are into the meat of the matter now. We have put forward some proposals, very reasonable proposals. We are…