St John workers going on strike later this month say it can be avoided if their employer simply lives up to the agreement they came to last year.
But the ambulance operator says it simply doesn't have the money, even with plans to cut about 100 jobs.
St John employees who are members of FIRST Union will strike for 24 hours on November 25, having given the two weeks' notice required of essential services on Monday.
Last year St John agreed to new pay rates, including penal rates for night and weekend work, that were meant to kick in on July 1 this year.
"St John kept saying they couldn't afford the shift pay claims," FIRST Union national ambulance coordinator Sarah Stone told Newshub, but the nine-month dispute was resolved when union members agreed to defer the new rates.
According to a release on St John's website, that agreement gave members of all three unions - FIRST, AWUNZ and NZAA - an average 6.5 percent pay increase and penal rates.
"It was last May that that agreement was signed," said Stone. "Unfortunately this year as it became closer to July 1 when the payments had to be made, St John contacted us two, possibly three weeks out and said 'we still couldn't afford to pay the shift pay'. We didn't accept it."
Stone says St John also wants to cut the pay of "emergency medical dispatchers and call takers in the comms centre by $10,000" and make changes to their role, but won't say what those changes are. St John also wants to remove a clause from the collective agreement which the union fears will allow bosses to change rosters "without consultation or agreement".
"Trust in the organisation is so, so low there is absolutely no way members can agree to this."
St John chief executive Sue Steen said its offer, already accepted by two of the three unions and currently before members for ratification, contains the "biggest pay correction and increase in the history of the ambulance service", made possible by a promise from the Government that it would "provide a sufficient contribution to enable the full implementation of the independent pay review".
"There remains a single unresolved issue over penal rates for our third union which will be heard by the Employment Relations Authority (ERA) and/or the Employment Court in 2021.
"We have made an offer to implement all recommendations in full within our affordability - including 15 percent penal rates and committing to maintain predictable rostering arrangements - so if increased penal rates were awarded it would not be possible to offer other parts of the remuneration progression package."
Stone says the dispute doesn't need to end up in front of the ERA or in court.
"They won't come to mediated bargaining. This strike action will force a mediated meeting. We've also asked the Minister of Health to intervene, to help try and restore the relationship."
Stone said morale at St John is already low, and they're having trouble filling jobs as it is. When qualified people leave they're typically replaced by people with less experience, she said, putting Kiwis in danger.
"A full strike is unheard of in New Zealand for ambulance officers. These are people who want to be at work, they love their jobs. They absolutely are dedicated to the work that they do."
Steen said St John is "working through the detail of how our emergency service will be delivered, including implementing additional cover, to lessen the impact on our patients and the public".
"Any industrial action must be undertaken in a safe and professional manner and St John is working to ensure there is limited negative impact to patients. We continue to work in good faith with all unions and hope to reach an agreement that meets the needs of all parties."