The two most senior Treasury and Finance officials have undercut the Government's claims of a $10 billion hole in the coalition's election policies.
In a dramatic move to distance themselves from the political battle, the officials released an unprecedented statement to reject suggestions they had examined proposed Opposition cuts.
It comes after shadow treasurer Joe Hockey's midweek release of $31.6 billion of savings. Coalition policies are being vetted by the independent Parliamentary Budget Office, then checked by three "eminent" economists.
But Kevin Rudd said a cursory examination of the figures showed holes that cast doubt on the coalition's entire agenda.
"It's a question of whether you're going to be truthful about that or not and what we're doing today is calling Mr Abbott on his truthfulness," he said.
"This is a $10 billion fraud on the Australian people which he has sought to put before them within the last 24 hours."
Treasury secretary Martin Parkinson and his Finance counterpart David Tune registered their concern yesterday at being politicised, saying they had not been asked to examine specific coalition policies and there were several reasons why similar policies could be costed differently.
"Different costing assumptions, such as the start date of a policy, take-up assumptions, indexation and the coverage that applies, will generate different financial outcomes," they said.
"The financial implications of a policy may also differ depending on whether the costing is presented on an underlying cash balance or fiscal balance basis."
Mr Abbott said the coalition's costings were accurate and it was the Prime Minister who was not being straight.
"Mr Rudd has got all of his own figures wrong and now he's getting our figures wrong, too," Mr Abbott said.
Earlier, Mr Rudd used Treasury and Finance work - done before the Government entered the caretaker period - to attack the coalition's numbers.
The Government has said the coalition's $5.1 billion saving from axing free permits associated with the carbon tax do not hit the Budget bottom line.
The coalition presented its savings on an accrual accounting basis after advice from the PBO. But the Budget bottom line is always represented on an underlying cash basis.
Although similar, the two measures can produce different results varying by billions of dollars. The Government said there was a $2 billion hole in the coalition's claimed $3.7 billion saving by axing the $500 low-income superannuation supplement.
A PBO costing suggests the coalition's plan to axe 12,000 public servants will save the Federal bottom line $5.2 billion, based on getting rid of 6000 people within nine months of taking over.
A Finance analysis of the same policy, released by the Government, suggests the saving would be $2.9 billion.