An eight-hour nurses' strike will go ahead on Wednesday, affecting all public hospitals and DHB facilities around New Zealand.

The New Zealand Nurses Union has "overwhelmingly" rejected a second DHB offer in multi-employer collective agreement (MECA) negotiations.

NZNO lead advocate David Wait said there was a high voter turnout from the 30,000 members who worked at DHBs. The ballot closed at noon.

"Members are facing serious nursing workforce issues, with pay rates that do not attract people into the profession or retain the people we have, and staffing levels which stretch them to breaking point, putting them and their patients at risk."

The Nurses strike would run from 11am to 7pm on Wednesday June 9, and would involve nurses, midwives and hospital assistants.

Some DHBs had requested more staff on Wednesday to provide "life-saving services" than they would normally roster, which Wait said was ironic.

"That staff levels are regularly below life preserving services levels should concern everyone," he said.

"We want the DHBs to be transparent about this being a large-scale problem where staff and patients are regularly put at risk.

"The DHBs have attempted to respond to this claim, but after years of delays and failed promises, members want to see some accountability on their part."

He said the second DHB offer was not significantly different to the first, and did not address the issues.

"Our members are genuinely concerned that nursing shortages would increase if it was accepted, and that standards of care for all in Aotearoa New Zealand would suffer as a result."

An added lump sum of $4000 - a part payment on back pay owed to members through the pay equity claim - was what distinguished the recent offer, he said.

The offer said the claims would be settled by the end of the year.

"Members know that lump sum payments do not lift actual rates of pay, which impacts on the long-term issues of a health system that values nurses and their work, attracts new people into the profession and encourages others back from overseas.

"They also find it unfair that they are being asked to wait for the pay equity process, when there is uncertainty about when this will happen or what the results will be."

He said it was "heartbreaking" that health workers were forced to choose industrial action, but did not rule out further strike action.

"Nobody wants this and the best way for future strikes to be avoided would be through a fair and decent offer," he said.

"We need the Government and the DHBs to come up with a profession-enhancing offer right now that truly recognises the contribution nursing staff make and that ensures the future of nursing for the wellbeing and safety of us all."

Canterbury and West Coast DHBs said they had contingency plans in place to ensure the public could still access the care they needed.

Acting chief executive for Canterbury and West Coast DHBs, Becky Hickmott, said urgent and emergency care would remain available throughout the strike, and 111 calls would be responded to as usual.

"This includes the Emergency Department, acute (unplanned) surgery, all intensive care units, cancer care and the Renal Dialysis unit," she said.

"There are close to 5000 nurses, midwives and healthcare assistants at Canterbury and West Coast DHBs, so the strikes are expected to cause significant disruption to non-urgent services in both regions.

"We apologise in advance for the disruption this strike will cause but we respect NZNO members' right to take industrial action and acknowledge that these key staff have a valued role as part of our health system."