British Prime Minister Liz Truss has quit after just 44 days in the job — sparking a new leadership contest for the fifth Conservative prime minister in just over six years.

Thursday’s announcement, which was largely expected after extraordinary scenes and controversies in the past fortnight, led Labour leader Keir Starmer to demand a general election “now”.

In what the BBC’s chief political correspondent Nick Eardley termed ‘‘ an unprecedented crisis in British politics’’, Ms Truss will remain in power until a leadership ballot is held in the next week.

It means whoever assumes the top job will be the third PM in 2022 following the resignation of the scandal-plagued Boris Johnson in July.

‘‘What happens now is the quickest turnover of power we have seen in modern times,’’ Mr Eardley wrote.

After a tumultuous seven weeks, including the death and burial of Queen Elizabeth and a swathe of contentious economic decisions, Ms Truss called a press conference outside the PM’s official residence at No.10 Downing Street.

Demonstrators protest opposite parliament after Britain’s Prime Minister Liz Truss resigned.  Photo: AAP

A national election does not have to be held until 2024, and under Conservative Party rules, Ms Truss technically was safe from a leadership challenge for a year.

But the rules can be changed if enough politicians want it – particularly after wide speculation that many had submitted letters calling for a no-confidence vote.

Ms Truss had been in office for just 45 days – the shortest tenure of any British PM, easily beating George Canning, who served for 119 days in 1827.

Her tenure will be marked by a botched economic plan unveiled by the government on September 23 that triggered financial turmoil and a political crisis that brought the replacement of Ms Truss’ Treasury chief, multiple policy U-turns and a breakdown of discipline in the governing Conservative Party.

Just five weeks into the job, amid speculation about her future and following volatility in financial markets, Ms Truss told the BBC’s political editor Chris Mason she was “sorry for the mistakes that have been made”.

Many Conservatives had said that Ms Truss must resign, but she remained defiant on Wednesday, saying she was “a fighter and not a quitter”.

An Ipsos poll conducted over the weekend found 53 per cent of people thought Ms Truss should quit and only 20 per cent would oppose her resignation.

The upheaval even led a tabloid, Daily Star, to pin the survival of Ms Truss against that of a lettuce.

It tweeted triumphantly on Thursday that ‘‘the lettuce has officially outlasted Liz Truss’’.

Tweet from @dailystar

Earlier, Conservative politician Simon Hoare said the government was in disarray.

“Nobody has a route plan. It’s all sort of hand-to-hand fighting on a day-to-day basis,” he told the BBC on Thursday.

He said Ms Truss had “about 12 hours” to turn the situation around.

The authors of the first biography of Ms Truss were scrambling to update their manuscript after the PM’s resignation, reported Bloomberg.

Tweet from @JAHeale

Newspapers that usually support the Conservatives were vitriolic.

An editorial in the Daily Mail was headlined: “The wheels have come off the Tory clown car.”

International Trade Secretary Anne-Marie Trevelyan, sent out earlier on Thursday to defend the government, insisted the administration was providing “stability”.

But she was unable to guarantee Ms Truss would lead the party into the next election.

“At the moment, I think that’s the case,” she said.

With opinion polls giving the Labour Party a large and growing lead, many Conservatives believed their only hope of avoiding electoral oblivion was to replace Ms Truss.

She faced more turmoil in Parliament on Wednesday night on a vote over fracking for shale gas – a practice Ms Truss wanted to resume, despite opposition from many Conservatives.

An opposition call for a fracking ban was easily defeated, but some MPs were furious that Conservative Party whips said the vote would be treated as a confidence motion, meaning the government would fall if it passed.

There were angry scenes in the House of Commons, with party whips accused of using heavy-handed tactics to gain votes.

Labour MP Chris Bryant said he “saw members being physically manhandled … and being bullied.”

Conservative officials denied any manhandling.

Rumours swirled that Conservative Chief Whip Wendy Morton, who is responsible for party discipline, and her deputy had resigned.

Hours later, Ms Truss’s office said both remained in their jobs.

The dramatic developments came days after Ms Truss fired her Treasury chief, Kwasi Kwarteng, a week ago after the economic package the pair unveiled spooked financial markets and triggered an economic and political crisis.

On Monday new Treasury chief Jeremy Hunt scrapped almost all of Ms Truss’ tax cuts, along with her flagship energy policy and her promise of no public spending cuts.

Who could replace Liz Truss?

https://www.bbc.com/news/uk-politics-63332047

The world reacts

US President Joe Biden said the US and Britain would continue their “close co-operation” following Ms Truss’s departure.

In a statement, Mr Biden thanked her for her partnership on issues including the Russian invasion of Ukraine.

“The United States and the United Kingdom are strong allies and enduring friends – and that fact will never change,” he said.

“We will continue our close cooperation with the UK government as we work together to meet the global challenges our nations face.”

French President Emmanuel Macron wished Britain a rapid return to stability.

Russia’s foreign ministry welcomed Ms Truss’s departure, saying she was a disgrace of a leader who would be remembered for her “catastrophic illiteracy”.

“Britain has never known such a disgrace of a prime minister,” Foreign Ministry Spokeswoman Maria Zakharova said.

The claim of illiteracy appears to refer to Ms Truss’s visit to Moscow as foreign minister, shortly before Russia invaded Ukraine.

-with agencies