The Coalition has fended off Labor attacks over its decision not to commit to its own budget bottom line when it releases its policy costings, with Opposition Leader Tony Abbott saying voters will be "able to do the arithmetic".

Opposition treasury spokesman Joe Hockey has again confirmed the Coalition will not provide a final budget figure because he does not trust the Treasury numbers used by the Government.

"We've been using the independent Parliamentary Budget Office to assist us, as well as other sources to assist us in helping to make sure that our numbers are far more robust than anything Labor has had," Mr Hockey told the ABC's AM program.

Mr Abbott has confirmed the Opposition will not release a final figure.

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"What we'll be doing in the campaign is we will be fully funding and fully costing all of our commitments and the budget bottom line will be better under the Coalition than under the Labor Party," Mr Abbott said.

"You'll be able to see, you'll be able to do the arithmetic and you will see that the budget bottom line will be better under the Coalition than under Labor."

Prime Minister Kevin Rudd has described it as a "stunning development".

"Warts and all, we've put our bottom line out there with the economic statement last week," Mr Rudd told constituents at a candidates forum in his Brisbane-based seat of Griffith this morning.

"What we'll spend, what we'll save, what the bottom line is, when we'll come back to surplus - it's there.

"The stunning development in the past few days has been Mr Abbott's treasury spokesman saying that in this election campaign, the Liberal Party will not put forward its own budget bottom line.

"That is unacceptable in a democracy.

"I had to do it in 2007. Everyone before us has had to do that.

"Is Mr Abbott simply trying to run away from where the $70 billion will be cut in basic services, in health, education, in jobs?"

PM's claim is 'complete bunkum': Hockey

Mr Hockey says the Prime Minister's claim that the Coalition is planning $70 billion in cuts is "complete bunkum".

"It is a falsified figure from Kevin Rudd and he needs to be called out on his lack of honesty," Mr Hockey said.

"Because he is not a person who is honest and he is a person that does not understand the economics of budget propriety.

"I'm not going to cop a lecture from the Labor Party about accuracy in numbers.

"I mean, their hypocrisy knows no bounds.

"And they've had every number wrong for six years.

"We're not going to cop a lecture from them about honesty and integrity, not from the Labor Party and not from Kevin Rudd."

Mr Rudd said the failure to state a final budget figure would leave the Australian people to conclude that the Coalition was not "fair dinkum".

Last week's economic statement released by the Government forecast this year's deficit will blow out by $12 billion to $30 billion and the 2014-15 deficit will more than double to hit $24 billion.

The budget figures will again be updated in the pre-election economic and fiscal outlook (PEFO), which must be released by Treasury and Finance by next Thursday.