Peter Dutton says he has the numbers to roll Turnbull as Prime Minister.
That statement comes after the former home affairs minister asked Turnbull to call a party room meeting where he will challenge him for the top job.
Cormann switching to Dutton's camp could be the key in the challenge happening.
"I don't think Peter Dutton would be doing this unless he had Mathias Cormann," Sky News political reporter Laura Jayes said.
"This is a big, risky move for Peter Dutton."
Mr Dutton tweeted his intentions this morning, but many speculated he did not have the required 43 signatures to get Mr Turnbull to call the meeting.
Sky News is reporting Dutton only has signatures of support from 25 MPs.
But Dutton briefly told reporters during a walk through Parliament this morning that he was confident he had the numbers.
"I wouldn't have contacted the PM if I didn't believe we have the majority support," he said in a brief statement.
Dutton has also released legal advice making it clear he is eligible to sit in Parliament after a "spurious and baseless" campaign against him.
"The timing (of the doubts) on the eve of current events in Australian politics is curious," he said.
Dutton addressed the media as he entered Parliament this morning, recapping what was said in his earlier tweet.
"I just wanted to make a couple of brief remarks and then I'm going to address the media later on," he said.
"As I put out, by way of statement earlier, 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.
"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."
Earlier, Turnbull was hit with further blows this morning with two of his ministers officially resigning.
The Liberals' leadership uncertainty entered its third day after a shambolic night.
MPs linked to Dutton attempted to launch a petition forcing Turnbull into a late night showdown.
It was a fizzer which only managed to antagonise some Liberals.
A furious senior Turnbull supporter told the Daily Telegraph Dutton's side had spread "lying propaganda" in an effort to pressure their colleagues into a vote, including rumours that key minister Mathias Cormann had flipped.
One Liberal MP has reportedly told the Australian Financial Review that the Whip's office has received four complaints from female MPs saying they felt intimidated when asked to sign the petition, which they refused to do.
Ministers Michael Sukkar and Zed Seselja have resigned, Sky News reports, while James McGrath resigned last night.
