The opposition has seized on reports the commission of audit has criticised Prime Minister Tony Abbott’s proposed paid parental leave scheme.

The commission’s interim report says the scheme is too generous in light of the budget’s unhealthy position, the Australian Financial Review said on Thursday.

The scheme, planned to begin in July 2015, will cost about $5.5 billion a year.

Labor finance spokesman Tony Burke has called on the government to release the interim report it received 13 days ago.

“You shouldn’t need a commission of audit to tell you that Tony Abbott’s paid parental leave promise is not sustainable,” he told Sky News.

Mr Abbott wants to give working women their regular wage for six months, capped at $75,000, after they give birth.

The existing paid parental leave scheme introduced by Labor government pays the minimum wage for 18 weeks.

The Labor scheme is funded entirely from the budget, while the Abbott version will be financed by a levy on big business.

Shadow treasurer Chris Bowen said Mr Abbott could not say the age of entitlement was over and then introduce the biggest entitlement scheme in Australia’s history.

He questioned why, if the commission of audit was secret, an element of its interim report was on the front page of a newspaper.

“My understanding is that only the prime minister, treasurer and finance minister have a copy and that it’s not been circulated among the cabinet,” Mr Bowen told reporters in Canberra, saying people could draw their own conclusions about the leak.