St John Ambulance is warning the public to be prepared for a reduced service due to increased pressure on resources.
Chief executive Peter Bradley said on Monday that Auckland staff are over-stretched and sending an ambulance to every 111 call will not be possible in the future.
Mr Bradley has been head of the emergency service for eight months and in that time has acknowledged that staff morale is low because they are overworked and there are not enough ambulances.
He is now concerned that paramedics are so busy they are not getting adequate breaks during their 12-hour shifts.
Mr Bradley said a major review of the service is looking at making the best use of its resources.
However, he said it is likely that the public would have to get used to a different kind of service that would involve a range of responses to emergency calls.
"We will be giving more advice on the telephone; we will be providing single responders to provide treatment in the home and we will be trying to refer patients to other parts of the health service.
"The days of dialling 111 and an ambulance coming to every call they're gone or going."
Mr Bradley stressed that, though the service will change, St John remained committed to making sure people with life-threatening emergencies get help as quickly as possible.
Three extra ambulances have been added to the service in recent weeks to alleviate some pressure.
The Ministry of Health has not yet been available for comment.
