Mason insisted the current offer on the table was an " excellent" one.
"In total, the offer would invest more than half a billion dollars in more staff and improving working conditions.
"It will also see the base pay rates of most experienced registered full-time nurses go from just under $66,755 now to $77,368 by December 2019.
"This offer is about much more than base pay rates. DHBs are committed to safer staffing, which includes a commitment to an additional 500 nurses to alleviate staffing concerns", she said.
Industrial services manager Cee Payne said a significant number of the members voted in favour of strike action.
"While the latest offer would see top-level nurses get a 15.9 per cent rise over three years, all other nurses would only get a 3 per cent increase a year over three years.
"Nurses and midwives do not trust that their work environment or patient care will improve in the short term.
"While the revised offer included new funding to address short staffing, concern remains that this may not be enough to make a real difference.
"We're going to do everything we can to see if we can get an improved offer out of mediation. We have the ability to conduct an online ballot before July," Payne said.
Health Minister David Clark said he was disappointed at the nurses' decision.
"The deal that's been rejected today is the largest nurses and midwives have been offered since their historic pay jolt 14 years ago under the last Labour-led Government.
"The proposal added an extra two steps for the longest-serving and most experienced nurses and would see most full-time registered nurses earning an extra $10,000 a year within 18 months. That is a far better deal than that offered under National."
Clark said he hoped "cool heads will prevail" and industrial action could be avoided.
Over the next two weeks, primary teachers and principals will also hold a series of nationwide union meetings to vote on the Ministry of Education's latest pay offers.
Teachers and principals want a 16 per cent increase over a two-year collective agreement, but the ministry has offered differentiated pay increases and a three-year term.
Liam Rutherford, the lead negotiator for the primary teachers' collective agreement, said if members voted to reject the offer, they would then vote on whether to hold a half-day stoppage on August 15.
Lead negotiator for the primary principals' collective agreement Louise Green said after a decade of neglect there were significant issues facing education.
That included a growing teacher shortage, stress, workload problems and under-resourcing and that needed to be recognised in the ministry's offer, she said,
Matt Simeon, executive member of the Western Bay of Plenty Principal Association, agreed.
"In general, most teachers and principals are pretty unsatisfied with the ministry's offer."