National has accused Labour of "shameful, mean and spiteful" politics after the government party blocked efforts to make paid parental leave more flexible.
A bill proposed by National's deputy Nicola Willis was voted down by Labour at its first reading in Parliament on Wednesday. All other parties supported it.
The legislation would have allowed parents to share their leave entitlement meaning they could take some time off together.
In an impassioned and scathing speech in Parliament, Willis said Labour's position had "insulted every parent in New Zealand".
"Labour has cast aside their values as they become desperate about the upcoming election. What they really wanted to do today was deny National a win. The sad thing is it's not about National. They're denying parents a win.
"What a shameful day."
Willis told MPs she was shocked that Labour had expressed such "patronising political views".
"I have birthed four children, and I find it insulting for members opposite to say it is wrong for men, for fathers, for lesbian partners to say, 'Well, actually, we think it's best in our family that we take paid parental leave at the same time'."
Labour backbenchers were left in the debating chamber to explain the party's opposition, arguing the legislation might not be in the best interest of babies.
"The mother might feel compelled to get back to work earlier," list MP Dan Rosewarne warned.
"The greatest gift we can ever give a child is time," Tukituki MP Anna Lorck said.
"They need at least that 26 weeks of one-on-one intensive care," Whangārei MP Emily Henderson said. "Let's have more ambition for our children and our families."
Labour's Hamilton East MP Jamie Strange - who was retiring at the election - struck a different tone, saying he personally would like the next government to revisit the idea.
"I think it's an issue that is worthy of working with officials on and actively looking into... so I do hope that in the next term of Parliament, that this is actively looked at."
Speaking to reporters after the debate, National leader Christopher Luxon said his party was on the side of parents.
"This is not a political bill at all. This is a common-sense bill... what we got from the Labour Party was mean and spiteful."
Willis told reporters Labour's position seemed to be that those who gave birth should stay at home for longer.
"That is a sentiment that belongs in the 1950s because actually parents are best placed to choose what is best for them and their families," Willis said.
Prime Minister Chris Hipkins said he was not ruling out making other changes to paid parental leave, but ultimately disagreed with National's approach.