Prime Minister Kevin Rudd says Tony Abbott's economic credibility rests on how he plans to pay for a $5.5 billion a year parental leave scheme.
The opposition leader says the scheme is his "signature policy" for the federal election.
Labor has raised concerns about its funding, with Mr Rudd saying it's unfair and unaffordable.
Under the scheme, working women get six months paid parental leave up to a total of $75,000 - based on a salary of $150,000 a year.
Mr Rudd said Mr Abbott was "out of touch" to compare the scheme with the aged pension.
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"The aged pension, which provides about $19,000 a year, he puts in the same category as a paid parental leave scheme which provides $75,000 for six months for millionaires," Mr Rudd said in the Victorian town of Torquay on Thursday.
"I just ask any Australian ... do they think that is fair?
"If this is Mr Abbott's captain's pick ... what would he do in his management of the general economy?"
The coalition says the policy has been fully funded and costed by the Parliamentary Budget Office, although the analysis hasn't been publicly released.
It plans to impose a 1.5 per cent levy on about 3000 large business, which Mr Abbott now says will pay for half the scheme.
Mr Rudd says there's a $3 billion gap, because the levy will only raise $2.5 billion a year.
But Mr Abbott says the remaining funds will come from scrapping Labor's existing parental leave regime and from "consequential adjustments" such as ending double dipping.
The prime minister said the coalition's political strategy was to hide the detail of its proposed budget spending cuts from voters before the election is held on September 7.
