Waitrose’s new head James Bailey, who joined from Sainsbury’s in April, said any regression from current high standards in the UK would be unacceptable and pledged that John Lewis’ food business would not sell products it deemed to be of an inferior standard.

“It would be simply wrong to maintain high standards at home yet import food from overseas that has been produced to lower standards. We would be closing our eyes to a problem that exists in another part of the world and to animals who are out of our sight and our minds. I feel sure customers will share our view,” he said.

More than a million UK residents have signed a petition calling for a ban on cheaply produced imports in any post-Brexit deals.