Former home affairs minister Peter Dutton, an ex-police officer and right-wing conservative, said he was confident he now had the numbers to unseat Turnbull, considered a moderate.
“Earlier this morning I called the prime minister to advise him that it was my judgement that the majority of the party room no longer supported his leadership,” he said in a brief statement.
“As such, I asked him to convene a meeting of the Liberal Party at which I would challenge for the leadership of the parliamentary Liberal Party.”
Turnbull survived a ballot on his leadership on Tuesday, winning the vote 48-35.
He is yet to publicly respond to the latest threat to his rule, although broadcaster ABC reported that he turned down the demand for another party meeting during the phone call.
But in a major blow, his influential Finance Minister Mathias Cormann, along with the employment and education ministers, said they no longer supported him.
They join at least 10 other ministers who have either resigned or offered to.
“It is with great sadness and a heavy heart that we went to see the prime minister to advise him that in our judgement he no longer enjoyed the support of the majority of members in the Liberal Party party room,” said Cormann, who used to be a trusted ally.
“It is in the best interests of the Liberal Party to help manage an orderly transition to a new leader.”
To force the issue, Dutton and his supporters must produce a petition signed by a majority of ministers, essentially saying they no longer had faith in Turnbull’s leadership.
Local media widely reported that such a petition was being compiled, but it was not clear how many names were on it.
Dutton, described by supporters as a pragmatic legislator who gets things done and by detractors as a racist who demonises refugees, quit his cabinet position after his first failed leadership bid.
If he became prime minister, Dutton said he would focus on lowering electricity prices, cutting immigration to ease population pressures and boost water investment to help drought-stricken farmers.
The turmoil came to a head after months of poor opinion polls and a revolt by fellow Liberal politicians on Monday against the prime minister’s plans to embed carbon emissions targets in law at a time of soaring power prices.
With its heavy use of coal-fired power and relatively small population of 25 million, Australia is considered one of the world’s worst per capita greenhouse gas polluters.
Dutton and his supporters, including former prime minister Tony Abbott who once described climate change as “absolute crap”, argue that keeping power prices down was more important than meeting Canberra’s commitment to slash carbon emissions by 26 percent by 2030.
The unrest is the latest chapter in a turbulent decade for Australian politics, with no leader managing to serve out a full term since John Howard lost the 2007 election.
And it has played into the hands of the Labor opposition, which has been making the most of the turmoil.
“Another day and another one of chaos from this government — a government that has effectively stopped governing because it’s too busy fighting itself,” said deputy opposition leader Tanya Plibersek.
“While this government fights itself, it’s not focusing on the issues that matter to Australian families. In contrast, Labor has been united and disciplined for five years.” DM
The average American woman today weighs as much as the average American man did in the 1960s.