Former UK Prime Minister Boris Johnson is privately urging Conservative MPs to back him for a dramatic return to Downing Street with a pledge that only he can win the Tories the next election.

Johnson is pressing former Chancellor Rishi Sunak to reach out and “get back together” in a remarkable olive branch after their public falling out at the top of government.

Sunak was pulling narrowly ahead of Johnson among Tory MP nominations today in a bid to claim the leadership victory he missed last month.

Liz Truss quit this morning after just 44 days in Number 10, accepting the near-total collapse of support among colleagues and becoming the shortest-serving prime minister in British history.

In an 89-second resignation speech in Downing Street, Truss admitted: “I cannot deliver the mandate on which I was elected by the Conservative Party.”

Her resignation triggered another leadership contest. A new PM will be selected from within Conservative ranks by next Friday.

Johnson - whose ousting as PM set off the disastrous chain of events leading to Truss’ downfall - will chuck his hat in the ring to seize back the top job, The Times reports.

Johnson - who is currently on holiday in the Carribean with his wife Carrie - believes his return would be in “the national interest” after weeks of market uncertainty saw the Pound plunge in value and mortgage rates soar.

The former PM is said to be consulting with other senior MPs and believes he can turn the party’s fortune around.

The news that Johnson, ousted from office after more than 50 ministerial resignations just three months ago, was considering joining the race immediately split Tory MP colleagues.

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There are doubts over whether Johnson can hit the 100 MP threshold given how support drained from him earlier this year. Party chiefs had to deny the rules were designed to block him.

Other frontrunners in the leadership contest are likely to be Sunak - who knifed Johnson in the back, leading to his resignation earlier this year - and Leader of the House of Commons Penny Mordaunt.

Truss, speaking on the steps of 10 Downing Street as her husband looked on, announced her resignation at 1.30pm (1:30am NZT) and said she had spoken to King Charles to let him know she planned to quit once a new leader was elected.

Who will take over as PM?

Johnson appears keen for another go as Prime Minister - but the British public will not have forgotten why he was axed in the first place.

His leadership was marred by a litany of scandals, the final straw being his admission that he promoted an aide to the post of deputy chief whip despite knowing he was facing groping allegations.

The PM had been told about the claims back in 2019 — and was even said to have remarked “Pincher by name, pincher by nature” — but still handed him the key job.

He was also fined by the police over “Partygate”, his attendance of parties in Downing Street - including his own birthday party - during the UK’s Covid lockdown.

Johnson was eventually turfed out of office by his own MPs, but he does have a swell of support among some party members who say that at least he has a mandate having been voted in during a general election.

He will face competition from former Chancellor Rishi Sunak, who also received a fine over Partygate.

Sunak is seen as more electable than many of his rivals, but is less popular with members of the party who accuse him of stabbing Johnson in the back.

He topped a poll of MPs during the last leadership contest but was comprehensively beaten in a vote of rank-and-file members by Truss.

Penny Mordaunt came third in that leadership vote and is also likely to throw her hat in the ring.

Mordaunt came to Truss’ defence earlier this week and is currently Leader of the House of Commons.

The runners and riders include Suella Braverman, who quit as Home Secretary on Wednesday, former Chancellor and Health Secretary Nadhim Zahawi and Kemi Badenoch, who also ran last time around. New Chancellor Jeremy Hunt has ruled himself out of the race and popular Defence Secretary Ben Wallace is likely to do the same.

UK Prime Minister Liz Truss and former UK Prime Minister Boris Johnson. Photos / AP / Getty Images

Truss resigns

Truss began her resignation speech by saying she came to power “at a time of great economic and international instability”.

She said the UK had been “held back for too long by low economic growth” and that she was elected by her party to change this.

“I recognise, though, given the situation, I cannot deliver the mandate on which I was elected by the Conservative party,” she added.

The immediate frontrunners to take over as Prime Minister are former Chancellor Rishi Sunak and leader of the House of Commons Penny Mordaunt, who were both beaten by Truss in September’s party leadership election.

The leaders of the three other main parties: Labour’s Sir Keir Starmer, the Scottish National Party’s Nicola Sturgeon and Sir Ed Davey of the Liberal Democrats have all called for a general election.

In what will likely be regarded as one of worst premierships in the history of the United Kingdom, Truss took just a matter of weeks to oversee a plunge in the value of the Pound, soaring mortgage rates and the worst polling numbers a governing party has ever seen.

She rode to a resounding victory in the Conservative Party’s leadership contest in early September by winning over grassroots members with a pledge to cut taxes and help families pay their energy bills at the height of a cost of living crisis.

But after the Covid pandemic saw government borrowing hit record levels, pledging to lend more to pay for her costly policies did not sit well with the markets.

She sacked her Chancellor Kwasi Kwarteng in an attempt to save her face, but by this point she had already lost control of her party.

A week later, her Home Secretary Suella Braverman resigned over a minor breach of Cabinet rules – and fired off a blistering letter directly challenging her ability to lead and heavily hinting she should quit.

Chaos broke out in the House of Commons later that evening Truss tried to force MPs to back a controversial vote on fracking that was seen as a vote of confidence in her leadership.

Economic chaos

When Truss and her first Chancellor Kwasi Kwarteng tabled radical plans for £45 billion (NZ$89b) in unfunded tax cuts, the markets were rocked, leading to a rapid fall in the value of the Pound and a sudden rise in mortgage rates.

Millions of homeowners now face paying triple the interest on their mortgage – something many simply will not be able to afford.

Plans to cut taxes for the richest in society, slash corporation tax for big businesses and ditch the end to a cap on bankers’ bonuses while offering a far more meagre tax cut to the poorest families played off badly with the public.

As pressure grew on Truss, she recalled her old friend Kwarteng from a trip to Washington, DC, to fire him in a desperate attempt to save her own skin.

But he found out he had been given the chop after reading about his sacking in The Times as he made his way from the airport to Downing Street.

As she fought to reunite her fractured party, Truss then parachuted in moderate Conservative Jeremy Hunt as her new Chancellor.

Who is in charge?

Hunt immediately ditched almost the entirety of Truss tax agenda and curbed her landmark energy bills support scheme, which did lead to the Pound’s brief recovery.

But Hunt’s move sounded the political death knell for Truss, who without a policy to stand on became a Prime Minister in name only.

Her own MPs started to call for her head as polls showed the Conservatives were as many as 30 points behind the opposition Labour Party in the polls.

By the time of her resignation, at least 16 Conservative MPs had publicly called for Truss to resign. In private, this number was far higher.

Even the King seemed to cast doubt over Truss’ ability to run the country.

As Truss entered the room at Buckingham Palace for their first-ever official audience on October 12, a toe-curling clip showed her saying: “Your Majesty. It is good to see you again.”

The King replied: “So you’ve come back again?”

Truss then said: “It’s a great pleasure.”

But then Charles, appearing to fill an awkward silence in front of the cameras, muttered: “Oh dear, oh dear.”

Night of chaos

Then on Wednesday afternoon, Home Secretary Braverman quit Truss’ Cabinet and blasted her on the way out.

In a blistering resignation letter, Suella Braverman slammed the PM and said she had “serious concerns” about the “direction of this government”.

“It is obvious to everyone that we are going through a tumultuous time,” Braverman wrote.

“I have concerns about the direction of this government. Not only have we broken key pledges that were promised to our voters, but I have serious concerns about this government’s commitment to honouring manifesto commitments.”

Braverman’s letter suggests she had earlier told Truss that she had sent an official document to an MP from her personal email account – in breach of Cabinet rules.

She wrote that this was a “mistake” that she must take responsibility for.

In a thinly veiled dig at Truss’ disastrous start as Prime Minister, she continued: “Pretending we haven’t made mistakes, carrying on as if everyone can’t see that we have made them, and hoping things will magically come right is not serious politics.

“I have made a mistake; I accept responsibility; I resign.”

Chaos broke out in the House of Commons that evening as Truss’ whips demanded Conservative MPs back the party in a controversial vote on fracking.

MPs reported seeing colleagues being physically manhandled into voting with the government in scenes of bedlam.

Truss’ chief whip and deputy chief whip both resigned … only to unresign hours later.

Reputation in tatters

Truss now holds the ignominious record of having the shortest time in office of any Prime Minister, taking the unwanted crown from George Canning, who died after 119 days as PM in 1827.

The Earls of Waldegrave and Bath served for four days and two days respectively in 1757 and 1746, but they were unable to form governments so they are not counted by most historians.

- Ollie Gillman, news.com.au