Boris Johnson has called on Theresa May to strike a Brexit trade deal that gives Britain the power to ditch EU laws, warning that failure to do so would render the UK a “vassal state” of Brussels.

In an interview with The Sunday Times, the foreign secretary said the government must seek to “maximise the benefits of Brexit” and failure to get an agreement that allowed divergence would mean the UK could not do “proper free trade deals” with other countries. In a move that will create nervousness in Downing Street, Johnson announced that he was planning a fresh intervention this week, penning the case for a “liberal Brexit” because the advantages of leaving have not been properly outlined for the public.

Philip Hammond, the…