Opposition Leader Tony Abbott says he does not apologise for the billions of dollars in cuts the Coalition would make to government programs if elected.

Leaked documents show the Coalition's razor gang is searching for $70 billion worth of savings, something the Greens say could send the economy into recession.

The $70 billion figure includes $27 billion from ditching the carbon tax and $11 billion from axing the mining tax.

It is also looking for savings to pay for $8 billion worth of tax cuts.

The Government says the Opposition will have to axe entire departments to pay for its promises.

But Mr Abbott says extra measures the Government is offering to offset the impact of the carbon price would not be needed if it is abolished.

"If you don't have the tax, you don't need the compensation," he said.

"Everything which the Government is promising is compensation for a bad tax that we don't need - that will damage Australians' cost of living."

Mr Abbott has told Macquarie Radio he would be prepared to call a double dissolution election over the carbon tax.

"We will oppose it in Opposition and we will rescind it in government, and if it needs a double dissolution, that's what it will take."

His treasury spokesman, Joe Hockey, is in charge of finding the savings; he too makes no apologies.

"Finding 50-, 60- or $70 billion is about identifying waste, identifying areas where you do not need to proceed with programs, and [I make] no apologies for it," he said.

'Process of natural attrition'

On ABC radio in Canberra, ACT Liberal Senator Gary Humphries admitted that could mean whole government departments are closed down to pay for it.

"We've made clear we intend to do with somewhat fewer public servants than we have at the moment, 12,000 fewer public servants in fact," he said.

"If that means consolidating some departments, well so be it."

Mr Abbott says cutting the number of public servants will not affect the quality of government services.

"I don't think that Commonwealth services are consummately better now than they were in 2007," he said.

"So given that there are 20,000 more public servants now than there were in 2007, we think that through a process of natural attrition, we can reduce that number by 12,000."

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Finance Minister Penny Wong says Mr Hockey needs to explain to Australians why their services would be cut under a Coalition government.

"Equally he should explain why is it that he just wants to unilaterally shut down government departments because they repudiate his economic thought bubbles," she said.

"That is clearly his agenda behind wanting to close the Department of Climate Change.

"He doesn't like the fact that that department, along with Treasury, says that his policy won't work and will cost Australian taxpayers more."

Senator Wong says Mr Hockey is not up to the job of being treasurer.

"He appears to be very good at creating budget black holes. We know that he started this electoral term with an $11 billion black hole, and all he has done is add to it," she said.

Credibility

Greens leader Bob Brown has joined the call for the Coalition to explain where the savings would come from if it took government.

"Seventy billion - that's hospitals closed, hospital wards closed, that's schools being shut, that's cutbacks in Defence, and we know already it's the closure of the Department of Climate Change," he said.

Senator Brown says the Opposition Leader has lost economic credibility.

"Would not Tony Abbott's ascent to government in these circumstances put Australia into recession?" he said.

"Don't say that lightly. But we're looking at real figures here coming from the Opposition itself. What will be the impact on the nearly one million small businesses?"

Senator Wong says global financial uncertainty has made things harder for the Government.

"We've been upfront that while the Australian economy has a lot of underlying strengths, our fundamentals are sound. Obviously the international situation does make it harder," she said.

"Our budget has us returning to surplus in 2012-13. We are simply saying the international situation makes it harder but our plan remains to return to surplus as we've outlined."

Community and Public Sector Union spokeswoman Nadine Flood says it is offensive for Mr Abbot to suggest cutting thousands of public sector jobs will not affect the quality of services.

"The Coalition is strident in their calls for no jobs to be lost due to a carbon tax but is quite happy to threaten thousands of public servants with the axe just to score a cheap political point," she said.

"If someone suggested slashing 1,000 jobs in Joe Hockey's electorate he'd be up in arms, but apparently if they're public sector jobs they don't count."