Former Opposition leader Malcolm Turnbull has unleashed an attack on his successor Tony Abbott, describing his climate change position as "bullshit".

In a strongly-worded blog entry posted this morning, Mr Turnbull personally attacks Mr Abbott for putting the party's integrity on the line, saying Coalition climate change policy has descended into "farce", because it does not have a policy.

He vows to cross the floor and vote for the Government's emissions trading scheme and urges his colleagues to follow him.

Mr Abbott declined to respond to the attack at a press conference in Sydney this morning, insisting his fight was with Prime Minister Kevin Rudd.

After ousting Mr Turnbull six days ago Mr Abbott withdrew Coalition support for an emissions trading scheme and said a Coalition policy would not involve any new taxes.

But in today's blog entry Mr Turnbull says emissions cannot be cut without a cost.

"While a shadow minister, Tony Abbott was never afraid of speaking bluntly in a manner that was at odds with Coalition policy," he writes.

"So as I am a humble backbencher I am sure he won't complain if I tell a few home truths about the farce that the Coalition's policy, or lack of policy, on climate change has descended into.

"To replace dirty coal fired power stations with cleaner gas fired ones, or renewables like wind let alone nuclear power or even coal fired power with carbon capture and storage is all going to cost money.

To get farmers to change the way they manage their land, or plant trees and vegetation all costs money.

"Somebody has to pay.

"So any suggestion that you can dramatically cut emissions without any cost is, to use a favourite term of Mr Abbott,'bullshit.' Moreover he knows it.

"It is not possible to criticise the new Coalition policy on climate change because it does not exist."

Mr Turnbull goes on to describe those who backed Mr Abbott's leadership as climate change sceptics.

"As we are being blunt, the fact is that Tony and the people who put him in his job do not want to do anything about climate change. They do not believe in human caused global warming.

"As Tony observed on one occasion 'climate change is crap', or if you consider his mentor, Senator Minchin, the world is not warming, it's cooling and the climate change issue is part of a vast left wing conspiracy to deindustrialise the world.

"The Liberal Party is currently led by people whose conviction on climate change is that it is "crap" and you don't need to do anything about it. Any policy that is announced will simply be a con, an environmental figleaf to cover a determination to do nothing."

He also attacked Mr Abbott for holding contradicting views on climate change and for reneging on the deal Mr Turnbull reached with the Government to pass the ETS.

"Tony himself has in just four or five months publicly advocated the blocking of the ETS, the passing of the ETS, the amending of the ETS and if the amendments were satisfactory passing it, and now the blocking of it," he says.

"His only redeeming virtue in this remarkable lack of conviction is that every time he announced a new position to me he would preface it with 'Mate, mate, I know I am a bit of a weather vane on this, but...'

"We have given our opponents the irrefutable, undeniable evidence that we cannot be trusted."

In a press conference this morning Mr Abbott brushed aside Mr Turnbull's attack and accused Mr Rudd of running away from Mr Abbott's proposal for a debate on climate change policy.

"My argument is with Kevin Rudd," he said.

"Kevin Rudd thinks that the best way to save the environment is to have a tax. I think that the best way to save the environment is to directly tackle our environmental problems.

"I'm very disappointed that Mr Rudd seems to be running away from debate about his emissions tax. Why is he running away from a debate?"

Asked by reporters if Mr Turnbull had spoken directly to him, Mr Abbott replied: "I think I know where people stand on this."

Liberal backbencher Dennis Jensen says he is "appalled" by Mr Turnbull's attack.

"It's taken him no time at all to undermine Mr Abbott," he said.

Dr Jensen also expects Mr Turnbull will continue to be outspoken from the backbench. "I think its the nature of the man. He doesn't take a beating well," he said.

Mr Turnbull's salvo comes amid reports that Opposition treasury spokesman Joe Hockey clashed with Mr Abbott several weeks ago over the cost of alternative climate change policies Mr Abbott was spruiking before he challenged for the leadership.

Mr Hockey is reported by Fairfax papers to have angrily claimed that Mr Abbott's proposals would cost $50 billion.

Speaking on AM this morning Mr Abbott said he was considering a range of options, but the final cost would be determined by what policy will be developed.

Climate Change Minister Penny Wong says Mr Turnbull's comments show nothing has changed in the Liberal Party.

"What we see today is both Malcolm Turnbull and Joe Hockey giving us a real insight into the chaos that is the Liberal Party climate change policy," she told The World Today.