The Labour MP whose bill extending paid parental leave has been vetoed by the government is disputing its claims about the costs.
Finance Minister Bill English said extending the leave from 18 to 26 weeks would cost taxpayers $278 million a year.
"In the context of the Budget, the government made some decisions about extending paid parental leave and this would be significant extra cost which doesn't fit within the Budget," said Mr English.
But Sue Moroney said official advice from the Ministry for Business, Innovation and Employment puts the annual cost at $122m, and she was challenging Mr English's use of the financial veto.
"It's not the first time that Bill English has been caught out exaggerating the figures for extending paid parental leave to 26 weeks and either he has issued the financial vetoes with incorrect information or he's deliberately misleading the New Zealand public on the issue."
Last year, Ms Moroney's first bill to extend paid parental leave from 18 to 26 weeks failed at the last minute when ACT's David Seymour voted with the government at the final reading - the votes were tied at 60 to 60 so the bill did not pass.
She was lucky enough to have the bill drawn from the ballot a second time this year, but despite having the numbers to get it into law, the Finance Minister foiled her plan.