BORIS Johnson has pulled out the race to become the next Prime Minsiter after admitting he cannot unite the warring Conservative Party.

The former premier said he had “reached out” to leadership rivals Rishi Sunak and Penny Mordaunt to see if they could work together in the national interest, but it had not proved possible.

In a statement, he said he had secured the 100 nominations needed to get onto the ballot paper, although the number who had declared support publicly was somewhat lower.

Mr Johnson said that if he stood there was a “very good chance” he would be back in Downing Street by the end of the week. 

He went on: “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.

“And though I have reached out to both Rishi and Penny – because I 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.”

Dorset MPs Sir Christopher Chope and Richard Drax said this weekend that they wanted Mr Johnson to return to Number 10 Downing Street. The county's other Conservative MPs - Tobias Ellwood, Simon Hoare, Sir Robert Syms, Michael Tomlinson and Chris Loder - are all nominating Mr Sunak.

Mr Johnson’s withdrawal leaves the election to replace Liz Truss as potentially a straight fight between Mr Sunak, the former chancellor, and Ms Mordaunt, the Leader of the House.

It could all be over a little after 2pm on Monday if Ms Mordaunt – who so far has fewer than 30 public declarations of support from MPs - fails obtain enough nominations to go forward.

Her supporters will be hoping that the departure of Mr Johnson will open up the contest, enabling her to make it onto the ballot paper.

If she does, MPs will hold an “indicative vote” to show who they support and there will then be an online poll of party members to decide the contest – unless one or other of the candidates stand down.

Many critics of Mr Johnson will be relieved to see him out of the race, fearing that it could plunge the party back into renewed turmoil.

While Mr Sunak – with more that 140 declarations of support according to some reports – is favourite to top the ballot of MPs, Mr Johnson’s supporters believed he would have come out top in the poll of party members.

It raised the prospect of another scenario – as with Ms Truss – where the choice of the members does not have the backing of MPs potentially leading to more turmoil and division at Westminster.