Malcolm Turnbull has said Scott Morrison likely played a double game during the Liberal Party leadership turmoil that saw Mr Turnbull ousted as prime minister.

Key points: Malcolm Turnbull says it is "possible, but it's unlikely" Scott Morrison was not playing a double game over the Liberal leadership

Malcolm Turnbull says it is "possible, but it's unlikely" Scott Morrison was not playing a double game over the Liberal leadership Turnbull also says Mathias Cormann urged him to give in to the right faction of the Liberal Party

Turnbull also says Mathias Cormann urged him to give in to the right faction of the Liberal Party According to Turnbull, Cormann referred to the Liberal's right faction as "terrorists"

As the treasurer in the Turnbull government, Mr Morrison presented as a loyal senior cabinet minister as Mr Turnbull's leadership crumbled.

Most prominently, when asked about his support for Mr Turnbull at a press conference, Mr Morrison put an arm around Malcolm Turnbull's shoulder and declared: "This is my leader and I'm ambitious for him."

But Mr Turnbull has now concluded it was likely Mr Morrison was working behind the scenes.

"He is a lifelong political operator and he is a control freak," Mr Turnbull told 7.30.

"So, the idea that those people that were voting for [Peter] Dutton tactically were doing so without his consent and approval is, well, it's possible, but it's unlikely."

Mr Morrison has declined to comment on Mr Turnbull's new book, A Bigger Picture, but has publicly denied working against the former prime minister, insisting he only put his hand up for the Liberal leadership after Mr Turnbull decided not to contest.

Turnbull told to 'give in to the terrorists'

Mathias Cormann and Scott Morrison both backed Malcolm Turnbull days before he was ousted from the prime ministership. ( AAP: Mick Tsikas )

In the middle of 2018, Mr Turnbull's position as prime minister was under increasing pressure from the hard-right faction in the Liberal Party and Mr Dutton emerged as the leading candidate for the anti-Turnbull camp.

By August 21, Mr Turnbull decided he had to act and called for a spill of the leader's position to try to end the rumblings.

He won the party room ballot, but Mr Dutton received 35 votes — more than anyone had expected. Mr Turnbull's leadership was mortally wounded.

Mr Turnbull alleges a bloc of Morrison supporters tactically voted for Mr Dutton in this first challenge, not because they wanted him as leader but to destabilise Mr Turnbull's leadership.

During this time, Mr Turnbull had a meeting with the Liberal's Senate Leader and Finance Minister, Mathias Cormann.

According to Mr Turnbull, Senator Cormann urged him to give way.

"He said, 'you have to give in to the terrorists'. His words," Mr Turnbull said.

Senator Cormann was referring to the Liberal Party's right wing.

"The way they operate is to basically bully and intimidate people," Mr Turnbull said.

"And what they do, they operate like a terrorist.

"Now, they don't use guns and bombs, I hasten to add.

"But it is the technique of terrorism, where you create enough mayhem, enough damage that people in the middle say: 'It's got to come to an end; how can I stop this terrible horror?'

"And they do that by giving in."

7.30 asked Senator Cormann for comment but was yet to receive a response.

Three days after Mr Turnbull instigated the first spill, Mr Dutton brought on a second.

With the leadership writing on the wall, Mr Turnbull did not stand.

Mr Morrison ran against Mr Dutton and then foreign minister Julie Bishop, emerging as the new leader and Prime Minister.

A week later, Mr Turnbull resigned from parliament. His political career was over.

'Very deep and very dangerous' depression

Malcolm Turnbull says the loss of Liberal Party leadership affected his mental health. ( ABC News: Jerry Rickard )

Mr Turnbull admits when he first lost the Liberal Party leadership to Tony Abbott in 2009, he did not handle it well.

"I started to sink into a very, very deep depression," he told 7.30.

"It was very deep and very dangerous."

He announced he would resign from parliament at the 2010 election.

"The moment I made that announcement, I knew it was a mistake," he said.

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"I then changed my mind and ran again.

"And I ran again, in large part, to survive because I felt this was something I could do to claw my way out of this terrible hole, the black hole I'd found myself in."

In 2018, he was better equipped to deal with the loss of leadership.

"I was bummed out, of course," he said.

"But I was also alert.

"I learnt that if you have a vulnerability to depression — and I think that most people probably do, to some extent — then knowing that is an enormous asset.

"Because if you know you've got that vulnerability, then when you feel it's coming on, you can do something to offset it.

"The other thing that I resolved was that I was going to make sure that when I stopped being prime minister, and that day was going to come one way or another, I would do everything I could to ensure I didn't fall into that abyss again.

"That's why I got straight out of parliament. I didn't muck around with indecision and tossing and turning."

Watch Leigh Sales' full interview with Malcolm Turnbull on 7.30 tonight on ABC TV.