Theresa May is heading for a showdown with her Cabinet next week when ministers will call for a “Plan B” alternative to her Chequers Brexit deal.

The Cabinet meeting on Monday, which was due to discuss migration policy, will now be dominated by Mrs May’s Salzburg humiliation.

The Prime Minister will be urged to offer an alternative to the proposal, agreed at her country residence in July, to keep the UK tied to the EU after Brexit – or face resignations.

One source said: “Monday is the crunch point. That’s when every Cabinet minister will have to look again and reassess like Boris [Johnson] and David Davis did.”

There was speculation in Westminster that Esther McVey, the Work and Pensions Secretary, might walk out of the meeting if no alternative to Chequers was presented.