Ambulance staff have been "told off" for claiming overtime after attending a cardiac arrest callout, according to their union.
The insight into the first responders' working conditions came as they began industrial action after seven months of unsuccessful pay negotiations.
New Zealand Ambulance Association chair Mark Quin told AM he had "never seen the ambulance service in such a crisis".
"We are actually going backwards."
Quin cited the incident last week where a crew went to support another crew attending an urgent cardiac arrest callout and then got "told off" for putting in for half an hour of overtime.
"I'm starting to ask questions around the whole culture from St John around financial viability," he said.
Quin said the level of service provided by St John was starting to decline.
"What we've watched, particularly in the last two years, is St John has started sending single crews to everything from a purple [very high priority] right down to a green [low priority] and frankly our officers have had enough of that."
Until a settlement is reached, staff will prioritise emergency and life-threatening calls and may be delayed attending lower priority jobs, which may be attended by only one officer.
Ambulance officers will also cease using their personal phones for St John operational needs; stop recording data; refuse to log in to a system that monitors St John operational vehicles; and stop doing remote triage - where if a patient is deemed to be non-urgent, they are then transferred to a paramedic to give health advice and options that may prevent the need for an ambulance.
Quin told RNZ these actions would put St John in breach of meeting certain standards and maintaining appropriate accreditation as an ambulance service provider, and make data that justified their funding inaccessible.
In a statement to RNZ, Hato Hone St John general manager ambulance operations Stu Cockburn said the organisation had a comprehensive contingency plan in place to ensure it continued to meet patients' needs.
"Our primary focus remains on patient safety and wellbeing," he said.
Cockburn said St John continued to work in good faith and was committed to reaching a settlement through ongoing negotiations.
