The former prime minister said that he “reached out” to his leadership rivals Rishi Sunak and Penny Mordant to see if they could work together in the national interest, but that proved impossible.

In a statement, he insisted he had secured the 100 nominations needed to get on the ballot – and that if he was nominated there was a “very good chance” he would be back in Downing Street by the end of the week.

He continued: “But over the last few days I have unfortunately come to the conclusion that this would simply be wrong. You cannot govern effectively unless you have a unified party parliament.

Former Prime Minister Boris Johnson arrived at Gatwick Airport in London after traveling on a flight from the Caribbean following the resignation of Liz Truss as Prime Minister.

“And although I reached out to Risha and Penny – because I hoped we could come together in the national interest – we unfortunately couldn’t work out a way to do that.

“So I’m afraid the best thing is that I don’t let my candidacy go forward and support whoever succeeds.”

Boris Johnson has the numbers to get on the ballot, supporters say