The gender pay gap is the biggest it has been in 10 years, according to new data from Statistic New Zealand.
The quarterly employment survey shows the gender gap has increased in the year to September by 1.3 per cent, from 12.85 per cent to 14.18 per cent.
Pay Equity Challenge Coalition said it was the biggest gap it had seen in a decade.
"It's a huge jump," said spokeswoman Angela McLeod.
"You would think that if the overall rate had gone up - quoted at 1.1 per cent - that the gender pay gap wouldn't be affected. You'd hope."
Although the coalition couldn't know for sure the reasons for the jump, McLeod said a higher proportion of women in part-time work had not helped.
"Unemployment has risen and probably an increase in part-time jobs.
"Female-dominated workplaces have been traditionally lower-paid, like carers and cleaners. In these lower-paid roles women are paid barely above minimum."
While the Government bases its measurements on data collected annually through the NZ income survey, the Statistics New Zealand quarterly employment survey provided more regular information, obtained from employers as well as employees, she said.
"The best [the gap] has ever been using the measurements we use is 12 per cent. It's still a gap and it's still unacceptable."
McLeod said the Equal Pay Act, passed in 1972, was not effective in the current economic climate, given the proportion of contract work.
"A couple of bills have been drafted, which will make it more transparent and therefore give women and men the available data to challenge their pay."
But waiting for the bills to be drawn was not enough, McLeod said.
"We want to see the Government take action - they could put those changes in themselves. The Government needs to take on board the international and New Zealand-based research and see how they could increase the productivity of the economy.
"The Government needs to take a long hard look at it."