Boris Johnson has challenged Theresa May to sack him by indicating that he has no intention of quitting despite saying that her favoured plan for post-Brexit customs is “crazy”.

Downing Street tried to side-step the confrontation with the foreign secretary after he said that her plans for a customs partnership would create a “whole new web of bureaucracy”. Friends of Mr Johnson said that he would not resign.

No 10 said that Theresa May continued to have full confidence in Mr Johnson but declined to say whether she had spoken privately with him about his comments.

The prime minister’s spokesman added that the entire cabinet had signed up to the two customs models put forward by the government last August. “Following last week’s sub-committee meeting,…