LABOR has seized on the coalition's inability to say how it will fund a $5.5 billion a year parental leave scheme as evidence spending cuts will be hidden until after the election.
Opposition Leader Tony Abbott and senior coalition frontbenchers could not specify how the scheme would be funded, or the role of the states, when quizzed about it on Tuesday.
The coalition, which opinion polls say will win government on September 7, offers women six months' leave on full pay, capped at $75,000, plus superannuation for each baby born from July 1, 2015.
Part of the funding will come from a 1.5 per cent levy on about 3000 companies, the scrapping of Labor's existing scheme and an end to "double dipping" by federal public sector workers.
Prime Minister Kevin Rudd said the coalition's budget management was a key question for voters.
"Every day this is like a train wreck unfolding," he said while campaigning in Brisbane.
"You've got huge challenges on the costings.
"Mr Abbott, because he believes he's already won this election, believes he can arrogantly not tell ordinary Australians where he's going to cut."
Mr Abbott said the scheme was "fully funded and fully costed" and rejected criticism it was a "Rolls Royce" scheme.
"This isn't a question of being generous - it's a question of being fair," he said.
However, he declined to say what proportion of the scheme would be funded by the company levy or commit to a cost-benefit analysis.
Shadow assistant treasurer and campaign spokesman Mathias Cormann said it had been costed at $6.1 billion over the forward estimates and at $5.5 billion a year "once it is in train".
Further funding details would be released "in the normal course of events".
"Contrary to what Labor is asserting, there will be no cuts, absolutely no cuts, in any other programs to fund our paid parental leave scheme," Senator Cormann said.
The states have been drawn into the debate because their public servants would have the option of shifting to the federal scheme, meaning there could be some shift of funds to the commonwealth.
West Australian Liberal premier Colin Barnett was adamant WA wouldn't contribute any money to the federal scheme.
However, the WA government on Tuesday said it understood a federal coalition government would fund the "gap" between its scheme and state schemes.
South Australian Labor premier Jay Weatherill said he was in the dark about the details, but Queensland and NSW have said they will back it.
Mr Abbott said he would have an "adult discussion" with the premiers after the election if he won.
Education Minister Bill Shorten said the release of the coalition's costings - expected in the final week of the campaign - would be a turning point for Labor's fortunes.
Meanwhile, a Liberal candidate whose personal website contained lewd and sexist content has resigned, after Mr Rudd challenged Mr Abbott to disendorse him.
Kevin Baker, contesting former Labor minister Greg Combet's NSW seat of Charlton, was forced to shut down his "Mini-Mods" forum site for car enthusiasts.
The site contained references to incest, domestic violence, racism and child abuse.
Finance Minister Penny Wong later said Mr Abbott's scheme was falling apart.
She said the Parliamentary Budget Office had found the net revenue impact of the 1.5 per cent levy would reap $4.7 billion over three years - $2 billion in 2015/16 when it is due to start.
"This is far less than the various figures used by the coalition over the last two days," she said in a statement.
The PBO costing indicated the levy would fund just 36 per cent of Mr Abbott's scheme, she said.