Former prime minister Bob Hawke has labelled Liberal leader Tony Abbott "as mad as a cut snake" for his opposition to the Government's climate change proposals.

Prime Minister Julia Gillard had asked Mr Hawke to launch a report into how climate change would affect Kakadu National Park, an initiative of the Hawke government 20 years ago.

Mr Hawke says he faced a fear campaign from the Opposition and mining companies over Kakadu similar to the one he says Ms Gillard is experiencing now over the carbon tax.

"It was going to end the mining industry as we knew it. Investors were going to be frightened off from Australia, they were going to pull up stumps and go away," Mr Hawke said outside Parliament House.

"Now you recognise exactly the same nonsense again."

"Now I don't mind Tony [Abbott], he's not a bad bloke, but as I said during the [election] campaign he's as mad as a cut snake - and he is, on this issue, totally irresponsible.

"This is a real issue about the sort of country this is going to be for his kids, grandchildren and so on."

Mr Hawke described the anti-carbon tax campaign as "cheap opportunism" with its claims that it will be the end of the mining industry, saying households and industry will be protected by compensation.

He defended Ms Gillard's about face on the tax because "circumstances in Parliament have changed since she made that [promise]".

"To trivialise it by saying 'No, the Prime Minister shouldn't do something about this because she made a statement in another circumstances and that should hamstring her forever more from making the right decision' - come on."

He said Ms Gillard and the Government had not handled the climate change debate "perfectly" but: "I can't remember a more difficult subject for a government to sell than this".

"You've got to think afresh, you've got no precedents to draw from, and you've got so many vested interests in the community who are looking at this issue through their own interest and not the national interest."

He said two years until the next election would give Labor plenty of time to win the debate.

"What the Government has done is really show the bad bits. The details of the good bits are still to come.

"As the details are unfolded, as the science here and around the world continues to confirm the necessity for action, my confidence in both Julia and the Government and in the Australian people leads me to the conclusion that this argument will be won."

Speaking earlier, Mr Abbott said people should not assume the carbon tax will become law, saying some Labor MPs are "very concerned" - especially those in coal-mining seats.

"They are speaking out privately and I think pretty soon they are going to be speaking out publicly.

"Let's not forget that this tax ultimately spells death for the coal industry. It spells death for the manufacturing industry, because the whole point of this tax is to say that the coal industry is not the foundation of a modern economy but is something that threatens the survival of our planet."

Mr Abbott said he was "really pleased" that 21 economists today signed a letter supporting climate change action, but said he wants "the people" to have their say too.

"Economists are important. Economists count. But every Australian is important, every Australian counts and that's why we need an election. The public needs to have their say on this tax, not just celebrities and not just economists."