There's been a major setback in the fight for nurses to fix the gender pay gap.

The Health Minister Andrew Little says the New Zealand Nurses Organisation has decided not to put a pay equity settlement to its members for a vote.

Some nurses were upset their pay rise would not be backdated to 2019.

The Union's now received legal advice on the deal saying the proposed settlement is unlawful.

RNZ health correspondent Rowan Quinn spoke to Māni Dunlop.