Britain must strike a strong trade deal with the European Union after Brexit and avoid becoming a subordinate state of the bloc, Boris Johnson said.

Failure to ditch EU law would make the United Kingdom a "vassal state," the foreign secretary told the Sunday Times newspaper.

Prime Minister Theresa May this week secured an agreement with the EU to move Brexit talks on to trade and a transition pact. But she must now unite her deeply divided cabinet over what trade deal Britain actually wants.

Writing in the Sunday Telegraph, Mrs May hit out at anti-Brexit campaigners who "want to talk Britain down".

She said: "Amid all the noise, we are getting on with the job.

"In the face of those who want to talk Britain down, we are securing the best and most ambitious Brexit deal for our whole United Kingdom.

"And my message today is very clear: we will not be derailed from this fundamental duty to deliver the democratic will of the British people."