The Federal Opposition has confirmed a report in which leaked party documents revealed it would cost the Coalition more than $38 billion to scrap the carbon and mining taxes.

The documents were obtained by Channel Seven and claim to show that the Coalition frontbench and senior advisers had been told of the figures in four separate meetings chaired by treasury spokesman Joe Hockey.

The Coalition's plan to dump the Government's carbon tax will cost $27 billion over four years, the documents say, while plans to wind back the Government's Minerals Resources Rent Tax would cost $11 billion.

The documents also revealed plans by the Coalition to fund $7 billion to $8 billion of personal tax cuts, while it would also have to find another $37 billion to pay for its promises from the last election.

Opposition finance spokesman Andrew Robb says it is a case of simple arithmetic and that scrapping the carbon and mining taxes would mean that an amount of revenue was lost.

But Opposition Environment Spokesman Greg Hunt says there would be no net cost to the budget from scrapping the carbon tax because the figure is based on how much revenue the tax would raise.

And he says that would be offset because the Coalition is scrapping the carbon tax compensation.

"Well actually there's zero cost to the budget of scrapping the carbon tax because, as has been known for 18 months, we'll neither tax nor spend. So there's zero cost to the budget," he said.

Mr Hockey was tight-lipped on the leaked documents, but Treasurer Wayne Swan was quick to seize on the revelations.

"[Opposition Leader Tony] Abbott has shown he is determined to talk down our economy, and now he has been exposed as having written a gigantic blank cheque," Mr Swan said in a statement soon after the report was aired.

"To allow themselves to dig such an incredible black hole shows just what a risk the Coalition would be to the economy at a time of global uncertainty."

Mr Swan said the revelation came on top of a humiliating $11 billion election costings black hole.

Mr Hockey said the Coalition had a record of delivering surplus budgets while Labor had delivered record deficits.

"Unlike the current Labor Government, the Coalition is prepared to do the heavy lifting and the hard work required to return the budget to surplus," he said.

ABC/AAP