BORIS Johnson has dramaticcally dropped out of the Tory leadership contest – ending speculation over a dramatic comeback to Number 10.

The former prime minister was teeing up a return to Downing Street following the resignation of Liz Truss after a chaotic six weeks in the job.

My Johnson had flown back from his holiday to begin gathering support from Tory MPs.

The former PM, who quit after a string of scandals, including being fined by police over Partygate law-breaking, had hoped to officially enter the race to replace Ms Truss on Monday– but needed the backing of 100 Conservative MPs to do so.

On Sunday night, Mr Johnson’s campaign team told supporters they have secured the 100 nominations needed from MPs for the former leader to get on the ballot paper.

Northern Ireland Secretary Chris Heaton-Harris sent a WhatsApp message to supporters confirming they have the numbers.

Mr Heaton-Harris told them: “OK everyone! Some very good news!

“Thanks to all your hard work, I can confirm we have completed all the paperwork (verified all nominations, with proposer and seconder) to be on the ballot tomorrow.”

But in a dramatic statement released on Sunday night, Mr Johnson confirmed he will not stand for the Tory leadership, saying that despite having the support of the MPs required to run, he had come to the conclusion “this would simply not be the right thing to do” as “you can’t govern effectively unless you have a united party in Parliament”.

He added that due to the failure to reach a deal with Rishi Sunak and Penny Mordaunt, “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,” the former prime minister said.

Mr Sunak, the only candidate to reach the 100 threshold needed to make it onto the ballot, formally announced he was bidding to become prime minister on Sunday.

Mr Johnson was dealt an early blow on Sunday when one of his key allies publicly backed Mr Sunak to become the next prime.

Suella Braverman, usually a staunch supporter of Mr Johnson, is supporting his rival to replace Liz Truss in Downing Street.

Ms Braverman, whose resignation as home secretary kickstarted the end of Ms Truss’s premiership, has now switched her support in favour of the former chancellor.

Writing in The Telegraph, she said: “I have backed Boris from the start.

“But we are in dire straits now.

“We need unity, stability and efficiency.

“Rishi is the only candidate that fits the bill and I am proud to support him.”

Ms Braverman added: “Things need to change.

“We, as a party, need to change. We need to provide leadership, stability and confidence to the British people.

“We cannot indulge in parochial or nativist fantasies.

“We need to move beyond Leaver or Remainer; One Nation or ERG; right of the party or left of the party; wets or thatcherites.

“Now, we all need to compromise and unite.

“One person can build that team: Rishi Sunak.”

The move will come as a big blow for Mr Johnson, who is yet to publicly evidence the 100 Tory MPs needed to get on the ballot to become the next prime minister.

Home Secretary Grant Shapps, has also backed Mr Sunak in the party’s leadership race.

Mr Shapps, who served in Cabinet under Mr Johnson tweeted: “We need someone who can provide stability and proven economic competence in these challenging times, and @RishiSunak is that person.

“That’s why I’m backing him in the Conservative leadership contest”.

On Saturday, Sir James Duddridge, a friend of Mr Johnson, said the former prime minister had the support of the 100 MPs required to reserve his place in the vote.

But Sunak supporter Richard Holden cast doubt on this suggestion, arguing that the equivalent number of public declarations had not been made “because they don’t exist”.

The former chancellor launched his second bid to become prime minister by claiming he would “fix our economy, unite our party and deliver for our country”.

He added: “There will be integrity, professionalism and accountability at every level of the government I lead and I will work day in and day out to get the job done.”

Mr Johnson's comeback bid was set against him facing an inquiry into whether he lied to the Commons over the Partygate scandal, for which he was fined by police.

If found guilty by the Commons Privileges Committee, he could face recall proceedings that would leave him battling for his seat in the Commons if he receives a suspension of 10 days or more.

Mr Johnson’s authority was dealt a further blow on Sunday after a former chief Tory Brexiteer warned Boris Johnson taking on a second term as prime minister would be a “guaranteed disaster”.

Steve Baker, the current Northern Ireland minister, has suggested Mr Johnson would be better suited as “chairman” of the Tory party.

Mr Baker, the former head of backbench Brexiteers, told Sky’s Sophy Ridge On Sunday: “I think it would be for the best if Boris did something big and statesmanlike.

“I mean, if he wants to come back as prime minister, he would need to do it after this privileges issue is settled.

“I think he’d make an amazing chairman of the party.

“But what we can’t do is have him as prime minister in circumstances where he’s bound to implode, taking down the whole government with him, and we just can’t do that again.” He added: “I’m afraid the trouble is because of the (Commons Privileges Committee) vote, Boris would be a guaranteed disaster.

“There’s going to be a vote before the House of Commons on this issue of privileges, whether he will deliberately misled the house.

“In that vote, it’s guaranteed there’ll be a large number of Conservatives who will refuse, as they see it, to lay down their integrity to save him, and at that moment his premiership will collapse.”

He added: “It’s a guaranteed nailed-on failure and we cannot allow it to happen.”