Almost 23,000 ambulance callouts a year in the three main regions are answered by a single paramedic, statistics from St John show.
The service has come under fire from the paramedics' union this week for understaffing.
The issue arose after a family member of a sick Huntly baby needing urgent
hospital treatment was forced to drive an ambulance manned by a single paramedic.
The ambulance was called on Friday, July 15, because the baby was having breathing difficulties.
When the paramedic arrived the 10-week-old baby had stopped breathing.
Rather than wait for backup the ambulance officer attended to the baby in the back of the ambulance and asked a family member to drive the vehicle to hospital.
St John chief executive Jaimes Wood said single-crewed vehicles responded to about 13 per cent of ambulance callouts throughout the country.
He said that equated to about 22,827 callouts in the country's three main regions - Northern, Central and Northern Region South Island.
Mr Wood said St John was undertaking a "gap analysis" to determine where the service fell short.
It would also apply for more funding from the Ministry of Health so it could employ more fulltime paramedics.
"I am hoping that these discussions will lead to a significant closing of the gaps," Mr Wood said.
About 2200 and volunteers and 700 fulltime staff work in ambulances around the country.
However, National Distribution Union organiser Neil Chapman said the service could no longer rely on volunteers.
The service's standard said ambulances responding to emergencies should have at least two crew, but Mr Chapman said that was not happening.
But Mr Wood said the standard was not mandatory and the service was working with the resources it had available.
"We have used policemen, firemen and the public before [to drive ambulances]," Mr Wood said.
"It is not ideal and not what we want to be doing, but what we do is still provide a very good ambulance service."
