Britain's governing Conservatives will hold a no-confidence vote in Prime Minister Boris Johnson on Monday that could oust him as Britain's leader.
Party official Graham Brady says he has received enough letters from lawmakers demanding a vote on Johnson's leadership to trigger one.
That happens if 54 Tory lawmakers, which is 15 per cent of the party's group in the House of Commons, write to Brady.
READ MORE: Aussies face long queues just to find out how passport processing going
"The threshold of 15 per cent has been passed," Brady said.
He said the vote would take place in person in the House of Commons on Monday evening UK time.
If Johnson loses the vote among the 359 Conservative lawmakers, he will be replaced as Conservative leader and prime minister.
If he wins, he can't face another challenge for a year.
Johnson has been struggling to turn a page on months of ethics scandals, most notably over rule-breaking parties in government buildings during COVID-19 lockdowns.
Late last month an investigator's report on what has become known as "partygate" slammed a culture of rule-breaking inside the prime minister's No. 10 Downing St. office.
READ MORE: RBA interest hike tomorrow will bring 'a lot of pain' to millions of Aussies
Civil service investigator Sue Gray described alcohol-fuelled bashes held by Downing Street staff members in 2020 and 2021, when pandemic restrictions prevented UK residents from socialising or even visiting dying relatives.
Gray said the "senior leadership team" must bear responsibility for "failures of leadership and judgement."
The prime minister said he was "humbled" and took "full responsibility", but insisted it was now time to "move on" and focus on Britain's battered economy and the war in Ukraine.
But a growing number of Conservatives feel that Johnson, the charismatic leader who won them a huge parliamentary majority in 2019, is now a liability.
If Johnson is ousted it would spark a Conservative leadership contest, in which several prominent government ministers are likely to run.
Conservative lawmaker Roger Gale, a Johnson critic, said "we have some very good alternatives to the prime minister so we're not short of choice.
"Any single one of those people in my view would make a better prime minister than the one that we've got at the moment," he told the BBC.
Discontent seems to have come to a head over a parliamentary break that coincided with celebrations of Queen Elizabeth II's Platinum Jubilee. For many, the four-day long weekend was a chance to relax, but there was no respite for Johnson, who was booed by some onlookers as he arrived for a service in the queen's honour at St Paul's Cathedral on Friday.
READ MORE: Australia 'hyping' warplane interception, Chinese state media says
Cabinet minister Steve Barclay, a Johnson ally, said toppling the leader now would be "indefensible."
"The problems we face aren't easy to solve," he wrote on the Conservative Home website.
"Democracies around the world are all currently facing similar challenges. But under Boris Johnson's leadership, our plan for jobs shows how we are navigating through these global challenges.
"To disrupt that progress now would be inexcusable to many who lent their vote to us for the first time at the last general election, and who want to see our Prime Minister deliver the changes promised for their communities."
