Boris Johnson has previously insisted that the UK will continue to ban the import of chlorinated chicken after Brexit

Boris Johnson championed American food and called for an end to “mumbo jumbo” and paranoia in a change of tone before Brexit trade talks.

The prime minister said that “pretty well-nourished” Americans disproved “hysterical fears” over the quality of agricultural produce from the US.

He insisted Britain would be “governed by science and not by mumbo jumbo” as the country negotiated a new trade deal following its exit from the EU.

When asked whether he believed that opposition to chlorinated chicken was irrational, Mr Johnson said that he accepted there were legitimate animal welfare concerns.

The UK and EU say there is no need to chlorinate chicken that has been properly produced. Previously Mr Johnson has insisted that the UK will continue to ban its