Theresa May was told by one of her former key advisers yesterday that her plan to rely on Labour MPs to get her Brexit deal through parliament was stupid and would fail.

Gavin Williamson, the defence secretary and Mrs May’s former chief whip who helped her to get elected, joined Andrea Leadsom, leader of the Commons, and Liz Truss, chief secretary to the Treasury, as the most outspoken opponents of the prime minister in a seven-hour cabinet meeting.

It ended with collective cabinet agreement to a plan to hold talks with Jeremy Corbyn, the Labour leader, but which dodged difficult questions about what happens next.

Mrs May appears to have put the government on course to remain in a customs union, thus breaking a