Shadow Finance Minister Andrew Robb believes Labor's deceit over the coalition's $31.6 billion of promised savings will be the last straw for many voters.
A week out from polling day, the government was trying to defend a Labor analysis that used earlier work conducted by Treasury, Finance and the Parliamentary Budget Office (PBO) to make cost assumptions about coalition policies.
It found a $10 billion hole in the coalition's proposed election savings.
Labor found fault also with the savings the coalition expects from shedding 12,000 public servants, ending the low income superannuation contribution and from abolishing the carbon tax.
But in an extraordinary move on Thursday, the heads of Treasury and Finance distanced their departments from Labor's statements, saying they had never assessed any coalition policies.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
PBO head Phil Bowen also said it was inappropriate to claim that the PBO has costed the policy of any other parliamentarian or political party.
Opposition Leader Tony Abbott said it was a "slap in the face" for the government and "simply wrong".
"This is an implicit statement that our costings are accurate," he told reporters in Melbourne on Friday.
Mr Robb said this was more about deceit than the costings process.
"For many people ... it will be the last straw," he told Sky News.
Former Liberal treasurer Peter Costello also weighed in, describing it as an attempted knockout that had badly missed.
"Kevin Rudd's gone for a big haymaker and hit the referee on the way through, and the referee has said foul," Mr Costello told Nine Network.
However, Prime Minister Rudd said the only fraud being perpetrated was that of Mr Abbott's refusal to release a full list of the coalition's's election promises until the eve of the September 7 election.
"It's not democratic, it is not open, and it perpetrated a continuing fraud on the Australian people," he told reporters in Perth.
Finance Minister Penny Wong seized on comments made by Mr Abbott that his full list of costings would be released towards the end of next week when also polices had been announced.
Senator Wong pointed out that Labor had released costings of 46 polices since its economic statement in early August - keeping to the Charter of Budget Honesty - while the coalition had lodged none.
Senior Labor minister Bill Shorten likened the opposition to David Copperfield the magician.
"They want you to look at everywhere except where the trick is happening," he told reporters in Melbourne.
But one business group has had enough, believing that while the government appears to have overplayed its hand, there is a growing weariness in the community with a campaign that seems obsessed with numbers over substance.
"The ongoing scramble by the major parties and bureaucrats to discredit each other on forecast figures and costings simply serve to underscore the lack of debate during this campaign" CPA Australia chief executive Alex Malley said in a statement.
"Let's hope the final week of this watershed campaign rises above the tired costings arguments and is characterised by a debate on a robust and visionary policy agenda for Australia's future."
