The New Zealand Nurses Organisation (NZNO) say a clear majority of its 32,000 members voted against the latest offer as it didn't improve "chronic and systemic safe staffing issues".

"Members have been clear from the beginning that their safety at work and the safety of their patients is a priority," lead advocate David Wait said.

"Nurses don't want more vague promises that the problem will be fixed in the future, which is what we have received once again."

However, Health Minister Andrew Little came out firing in response to the ballot's rejection, saying "the Nurses Organisation rejected their own proposal".

He released the terms of the rejected deal, showing nurses would have received annual pay rises of between 3.2 per cent and 5.37 per cent.

Those rises included immediate lump sums of $NZ7200 ($A6800).

Two strikes - for eight hours on August 19 and a 24-hour stand-down across September 9 and 10 - are set, testing the credentials of Ms Ardern's government.

Last month, tens of thousands of nurses walked off the job in the first national nurses strike in a decade.

Many marched on parliament house in Wellington for a rowdy protest on the lawns.

Nursing roles in NZ pay significantly less than similar positions in Australia, making a switch across the Tasman an attractive prospect for Kiwis and leading to shortages.

Mr Little, a former union organiser who led Labour prior to Ms Ardern, said he wouldn't wait for a union agreement to start to fix the short-staffing problems or to begin a new recruitment campaign.

"It is desperate and the nurses are desperate. So we will just do those things," he said.

A new government offer is expected prior to the August strike.

Australian Associated Press