Malcolm Turnbull has unleashed on Scott Morrison in a brutal new interview in which the former Liberal leader also likened his climate change denying colleagues to "terrorists".

Speaking to the BBC, the former Liberal prime minister said he was at a loss to explain his successor's conduct including downplaying the bushfire crisis and heading on a Hawaii holiday.

“I do not know why Scott Morrison has acted the way he has. I mean to be very frank with you, I worked with him very closely, I’ve known him for 20 years at least, and I can’t explain his conduct,” he said.

“I can’t explain why he didn’t meet the former fire commissioners who wanted to see him in March last year to talk about the gravity of the threat.

“Everybody knew we were in a very dry time and as a consequence the fire season was likely to be very bad. So rather than doing what a leader should do and preparing people for that, he downplayed it and then of course chose to go away on holiday in Hawaii at the peak of the crisis.

“It’s just not consistent with the way in which a Prime Minister would or should act.”

Last year, The New Daily revealed the Prime Minister had embarked on a secret trip to Hawaii in the middle of the bushfire crisis.

Mr Turnbull said Mr Morrison downplayed it, and at times discounted the influence of climate change.

"Which is just nonsense from a scientific point of view. So that's misleading people," he said.

‘War on science’: Malcolm Turnbull says Scott Morrison has misled the nation on bushfire crisis_1
Inset: PM Scott Morrison was caught hamming it up with holidaymakers in Hawaii.

Despite being held hostage by a rump of climate change denialists when he led the Liberal Party, Mr Turnbull urged his successor to show some spine.

“How many more coral reefs have to be bleached? How many more million hectares of forest has to be burnt? How many more lives and home have to be lost before the climate change deniers acknowledge they are wrong?” he said.

“If a country like Australia is not prepared to grapple with these issues seriously – itself being on the front line of the consequences and being an advanced, prosperous, technologically sophisticated country with the means to do so – why would other countries take the issue as seriously as they should?”

The former prime minister, who has a new book out this year, also slammed the US President Donald Trump for playing a "very destructive" role in the climate debate.

"Trump makes no bones about it. He says global warming is rubbish," Mr Turnbull said.

"Trump is trying to put a brake on global action to reduce emissions. The lack of American leadership is extremely damaging.

‘War on science’: Malcolm Turnbull says Scott Morrison has misled the nation on bushfire crisis_2
Inset: PM Scott Morrison has had several bushfire recovery roundtables in Canberra. Photo: AAP

Mr Turnbull also accused his own predecessor, Tony Abbott, of being the nation's most prominent climate denier in Australian politics, who was joined by others in a shameful "war against science".

"It is an extraordinarily irrational and self-destructive approach," Mr Turnbull said.

"The right [wing] in the Liberal Party essentially operate like terrorists," he said.

"Now I'm not suggesting that they use guns and bombs or anything like that, but their approach is one of intimidation.

"And they basically say to the rest of the party… if you don't do what we want, we will blow the show up. Famously one of the coup leaders said to me, 'you have to give in to the terrorists'."