Shadow treasurer Joe Hockey has defended the coalition's $31.6 billion of proposed savings, saying Labor's accusations that they don't add up are "dead wrong".

Labor says an analysis, using previous advice from Treasury, Finance and the Parliamentary Budget Office (PBO), of the costings released on Wednesday showed a $10 billion "black hole".

Mr Hockey called it "even more lies" from a desperate party that has nothing positive to say before the September 7 election.

But Prime Minister Kevin Rudd questioned the honesty of Opposition Leader Tony Abbott.

"It is quite clear that there is now a massive $10 billion hole in the $30 billion they are claiming," Mr Rudd told reporters in Melbourne on Thursday.

"This is a $10 billion fraud on the Australian people."

Mr Abbott said the figures were produced by the PBO and validated by three distinguished public finance experts - Geoff Carmody, co-founder of Access Economics, Len Scanlan, former Queensland auditor-general and Professor Peter Shergold, former secretary of the department of Prime Minister and Cabinet.

"Let's be very clear, Mr Rudd has got all of his own figures wrong, now he is getting our figures wrong too," Mr Abbott told reporters in Sydney.

"When it comes to budget figures, when Mr Rudd's lips are moving you know he is not telling the truth."

Labor pointed out the department of Finance says the coalition's plan to reduce the public service by 12,000 staff would save $2.8 billion, not the $5.2 billion claimed by the coalition.

Additionally, in a document from May, the PBO estimated more than 20,000 jobs would need to go to deliver $5.2 billion.

Mr Hockey said this advice not only uses quite different assumptions, it pre-dates the Pre-election Economic and Fiscal Outlook and his own costings from the PBO.

"It is plainly dishonest of the government to assert that its figures represent a costing of the coalition's position," he said in a statement.

Labor also raised questions over the coalition's assumptions over not proceeding with Labor's low income superannuation contribution, and savings measures linked to scrapping the carbon tax.

Treasurer Chris Bowen said history was repeating itself after the coalition's 2010 costings were found to have an $11 billion black hole after the election.

The coalition has promised to release a full list of its election promises, both savings and expenditure, next week.

The final week of the campaign will also feature the release of the national accounts for the June quarter on Wednesday, which looks set to be a subdued result according to new data.

Capital expenditure rose four per cent in the quarter, but the component that feeds into growth, plant and equipment, fell for a third consecutive quarter, down 1.2 per cent.

Taken together with data that showed soft non-residential building, TD Securities strategist Alvin Pontoh downgraded his quarterly growth forecast to 0.4 per cent from 0.6 per cent previously.

This would leave the annual rate at 2.3 per cent compared to 2.5 per cent as of March.