Photo: RNZ / Marika Khabazi
*Correction: This story has been updated to clarify the actions withdrawn by ambulance staff during the industrial dispute.
The ambulance drivers' union says industrial action will continue until a settlement is reached - and could go on for 12 months.
Hato Hone St John said urgent and life-threatening emergencies would be prioritised, and it had contingency plans in place to ensure it continued to meet patients' needs.
New Zealand Ambulance Association chairman Mark Quin said the union had reached an impasse with St John over pay negotiations.
He said the collective employment agreement expired six months ago, and there was still no resolution in sight.
Quin said these actions would be the first of many.
"The action is continuing until we reach the settlement, so it will continue to such a time that there is a settlement on the table," Quin told Morning Report.
"It could be 12 months - it's up to St John and Health New Zealand to sort out the funding issues, because they seem to be in loggerheads with each other at the moment."
St John ambulance staff strike over pay
The union gave two weeks' notice of strike action.
During the action ambulance officers will cease using their personal phones for St John operational needs; stop recording data; refuse to login 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 said these actions will make St John in breach of meeting certain standards and maintaining appropriate accreditation as an ambulance service provider, and make data that justifies funding for St John inaccessible.
"At the end of the day, we do not want patients to suffer - particularly as we go into winter," Quin said.
"We are just trying to make our voice heard, and our issues heard - we are six months, soon to be seven months, in breach of the contract."
He said crews will be responding to serious and urgent calls, such as cardiac arrests, as quickly as usual, but there may be delays on lower level calls.
In a statement, 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 and was committed to reaching a settlement through ongoing negotiations.
RNZ is contacting St John for comment on whether less urgent calls may be delayed.