Boris Johnson's allies have raised concerns that he could be the victim of a Cabinet reshuffle as Theresa May declined to say he will stay on as Foreign Secretary after the election.

A friend of Mr Johnson told The Daily Telegraph that "clouds are gathering" and they are "worried" for his future if Mrs May secures a landslide election victory.

"If she has a massive majority she may not need him," the ally said. "Boris selling Brexit might not work anymore - if she has a massive majority she sells Brexit."

The Prime Minister said that Mr Johnson is doing a "great job" but declined to comment on whether he will remain Foreign Secretary following a series of briefings against him by Cabinet colleagues.