The government's fiercely contested Pay Equity Bill has passed its first reading in parliament amid strident protest from opposition MPs.
The bill sets the rules around future pay equity claims, and follows on from the historic $2 billion care worker settlement that came into force on July 1.
The government says it will ensure workers in female-dominated occupations are treated fairly in future, but opponents say the legislation is designed to shut down claims.
"It will make a vital contribution to closing the gender pay gap," Workplace Relations Minister Michael Woodhouse said when he opened the first reading debate.
"When it's passed it will ensure that female-dominated occupations that have historically been subjected to gender pay discrimination are in future paid fairly."
Labour leader Jacinda Ardern said the care worker settlement would not have happened under the bill.
"I absolutely understand this bill - he has removed the flexibility that led to the success of that case," she said.
"The bar that has been set makes it absolutely untenable for women, especially those outside a union workplace, to establish a case."
The Public Service Association, which is leading a campaign against the bill, says it is "a wolf in sheep's clothing".
"It is a completely deliberate and calculated move by the government to clamp down on future claims," the PSA said in a statement.
"It is being incorrectly presented to the New Zealand public as a pathway to equal pay. In fact, it will make it significantly more difficult."
The bill passed its first reading today by 60 votes to 59. Most of the debate took place on Tuesday. National, ACT and United Future supported the bill, while Labour, the Greens, NZ First and the Maori Party opposed it.
The bill has been sent to a select committee for public submissions.