The prime minister said he would “walk away” from negotiations, agreeing the National Health Service is “more important” than a trade deal, before adding “there is no point in continuing the conversation”.

He continued: “Why on Earth would we do something as stupid as that? We are going to keep the NHS, properly fund it.”

The Conservative Party has repeatedly been attacked for its funding and position on the NHS, with Labour saying it has “proof” the party plans to put the NHS “up for sale”.

It comes as a 451-page dossier showed talks, held when Theresa May was in Downing Street, saw UK officials discuss the NHS with their American counterparts.