"We're working our way through it, in terms of Budget bids. Twenty-six weeks is not affordable, but we do think some extension might be."
New Zealand's paid parental leave is among the lowest in the OECD, and is similar to entitlements in nations such as Algeria and Malta.
Australia gives mothers 18 weeks, and Prime Minister Tony Abbott is planning to expand the scheme next year to 26 weeks.
Parent advocacy groups in New Zealand urged MPs to support Ms Moroney's bill yesterday. A coalition of health organisations and lobby groups called 26 for Babies said new costings showed extending paid leave was significantly more affordable than the Government believed.
Finance Minister Bill English contested this, saying Labour had based estimates on the initial cost of rolling out the scheme, not the cost once it was fully implemented. He said it would require the Government to borrow $500 million over four years.
Treasury advice to the committee showed once Ms Moroney's bill was fully implemented, it would cost an additional $138 million a year.
It would also make savings of at least $28 million because of reductions in tax, welfare payments and childcare subsidies.
Mr English said a Government proposal would be affordable and fair, and would keep in mind the fact that only 40 per cent of families who had babies took paid leave.
In December, National requested a later deadline for the select committee's report on the bill to give the party time to reconsider its position.
But the committee came back with no amendments yesterday, prompting Ms Moroney to accuse National of delaying tactics.
"I agreed to that extension in good faith, but National members introduced no amendments and then voted down the work the select committee had done," she said.
Of the 3,809 submissions to the committee, 99.6 per cent wanted paid leave extended to 26 weeks. If the bill was accepted, parental leave would be extended by four weeks each year over three years.