The Government is changing the law so the earnings of minimum wage workers will be able to be calculated fortnightly, Radio New Zealand reports.
Under the Minimum Wage Act, they can now only be calculated hourly, daily or weekly.
Labour Minister Simon Bridges said many workers are on fortnightly rosters with a different number of hours each week. The change means employers will not end up having to pay staff for hours they did not work.
But the Labour Party believes introducing a fortnightly minimum wage rate will allow employers to exploit low paid workers.
Labour's Associate Labour Issues spokesperson, Darien Fenton, said that will allow farmers to continue having low-paid employees work extremely long hours.
The law change has come about because the Government has caved in to lobbying from farmers, she said.
Federated Farmers said the change means workers can be paid for 80 hours a fortnight rather than 40 hours a week.
The changes come into effect at the end of June.