Theresa May is facing the threat of Cabinet resignations after she accepted EU demands that there will be no time limit on her controversial Brexit backstop plan.

The Prime Minister told her Brexit “war Cabinet” on Thursday afternoon that a proposal to keep Britain in a customs union with the EU until a trade deal can be agreed will have no end date, leading to fears the arrangement could become permanent.

At least three eurosceptic Cabinet ministers are said to be considering quitting over the latest concession, which appears to contradict Mrs May’s promise earlier this year that the backstop would expire “at the very latest by the end of December 2021”.

Penny Mordaunt, the International Development Secretary, and Esther McVey, the Work and Pensions Secretary, have both refused to endorse the Prime Minister's Chequers plan. Andrea Leadsom, the Leader of the Commons, is also understood to have significant concerns.

The three were not invited to the meeting, but several ministers who were present are understood to have raised concerns including Jeremy Hunt, the Foreign Secretary, Liam Fox, the International Trade Secretary, Dominic Raab, the Brexit Secretary, and Michael Gove, the Environment Secretary.

One source said that Eurosceptic ministers believe that the plans represent a "betrayal" of Brexit. "It's not what people voted for," the source said.