The former PM says he had the support of enough MPs but there needs to be “a united party in Parliament”.
Image source, ReutersBoris Johnson has pulled out of the Conservative leadership race, saying he had the support he needed but “it would simply not be the right thing to do”.
Former chancellor Rishi Sunak and cabinet minister Penny Mordaunt remain in the contest.
In a statement, Mr Johnson said there was a “very good chance” he would have been successful, and “back in Downing Street on Friday”.
But he said there needed to be “a united party in Parliament”.
Mr Johnson said he had been attracted by the contest because: “I led our party into a massive election victory less than three years ago – and I believe I am therefore uniquely placed to avert a general election now”.
He said: “I believe I am well placed to deliver a Conservative victory in 2024 – and tonight I can confirm that I have cleared the very high hurdle of 102 nominations, including a proposer and a seconder, and I could put my nomination in tomorrow.
“I led our party into a massive election victory less than three years ago – and I believe I am therefore uniquely placed to avert a general election now.
“I believe I am well placed to deliver a Conservative victory in 2024 – and tonight I can confirm that I have cleared the very high hurdle of 102 nominations, including a proposer and a seconder, and I could put my nomination in tomorrow.
“There is a very good chance that I would be successful in the election with Conservative Party members – and that I could indeed be back in Downing Street on Friday.
“But in the course of the last days I have sadly come to the conclusion that this would simply not be the right thing to do. You can’t govern effectively unless you have a united party in parliament.”
He said he had reached out to both Mr Sunak and Ms Mordaunt because he had “hoped that we could come together in the national interest – we have sadly not been able to work out a way of doing this.
“Therefore I am afraid the best thing is that I do not allow my nomination to go forward and commit my support to whoever succeeds.
“I believe I have much to offer but I am afraid that this is simply not the right time.”
According to BBC research, Mr Sunak has the backing of 147 MPs, while Ms Mordaunt has 24.
Candidates need the support of at least 100 MPs to go forward in the ballot.
Nominations close at 14:00 BST on Monday.