The Green Party would require all workplaces to measure and disclose the pay gap between men and women employees if it gets into government.

The party released its pay equity policy today, saying it would ensure that women were treated equally and paid better.

Co-leader James Shaw said his party would require employers to collect data on the wage rates for men and women, by adding gender to pay roll data.

If any employee or union asked for the information, the employer would have to provide anonymised and aggregated data about the pay and gender of other people doing the same work.

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Seeing the difference in pay rates in black and white would encourage employers to change their approach, the party said.

"This will help remove the secrecy that that has meant some women continue to be underpaid for the valuable work that they do."

The policy was already used in Norway, Sweden and Finland, where income equality is among the best in the world.

The Greens would make public sector bosses responsible for achieving pay equity within government departments, with a target of equal pay by 2025 written into their contracts.

The party also wants to amend pay equity laws to match the recommendations of the Joint Working Group on Pay Equity Principles.

The working group provided principles for employers and employees in resolving pay equity claims and a process for them to follow.

But the Greens say a National Party bill based on the working group's recommendations had actually created more hurdles to women being paid fairly.

The Greens will reverse the onus onto employers to prove that they paying women a fair wage, rather than placing that onus on the worker.

The Greens policy also includes a new expert body to help equal pay claims progress quickly, more funding for the Ministry for Women, and a guarantee that the Minister for Women gets a seat at the Cabinet table by right, not just because they hold other senior portfolios.

Deputy Prime Minister Paula Bennett currently holds the women's affairs portfolio.