The Fire Service is increasingly being sent to emergencies when an ambulance has been requested, statistics show.
In 2003-4, fire crews were called out to medical emergencies 2177 times.
At the last count for 2008-9, this number had risen to 5285.
These callouts took place when ambulance services were delayed or unable to respond to a medical emergency, or fire services were needed to assist existing ambulance services.
They did not include instances where fire services were called to provide specific rescue equipment, such as rescuing people from car crashes, or to assist members of the public in life threatening situations.
Under a national agreement signed between fire services and St John ambulance in 2005, if the fire service can arrive at a medical emergency before an ambulance, then they are sent.
Jon Graham, from the department of operations and training at New Zealand Fire Service's national headquarters, said across the total workload of the fire service, 14 per cent of the callouts involve the fire service working with ambulance teams.
"It's a reasonable amount. It has been increasing over the years," he said.
Mr Graham said there were three types of medical emergency where fire crews are called, and a "first response" callout is the one which causes the most confusion.
"First response is where ambulance gets there but they may be a bit far off - we're more likely to get there first," he said.
"Some people are confused but they're happy to get any help."
There were more medical callouts where the ambulance stations were spread thinly on the ground, he said.
"Especially in the more remote locations this is definitely the case."
However he said they were there to assist, not be a substitute for ambulances.
"We're not replacing ambulances, we're just there to lend a hand."
Statistics from the fire service showed first-response type medical callouts had increased in every region from 2003-4 to 2008-9.
Nationally, the percentage of medical callouts out of all fire calls had more than doubled in the last six years, from three per cent to seven per cent.
Some of the areas which showed the biggest percentage increases were Taranaki (up from 1 per cent to 7 per cent) Marlborough (from 1 to 4 per cent) Otago (from 3 to 10 per cent) Waikato (from 5 to 12 per cent) Northland (from 3 to 8 per cent) and Bay of Plenty (from 4 to 8 per cent).
Only one region showed a decrease in the last six years, Gisborne (down from 9 per cent to 8 per cent).
St John operations director Tony Blaber said ambulance services are ill-equipped to deal with the high level of callouts.
"Ambulance services in New Zealand are not sufficiently funded to meet the ever-increasing demand," he said.
"The fire service is substantially better resourced, including the provision of fire stations."
He said St John's 2007 submission to the Health Committee noted ambulances respond three times more often than the the fire service and the per capita funding is less than 50 per cent of fire service funding.
National Distribution Union ambulance representative Craig Page said the agreement is a symptom of the problem of "systematic and structural problems" with the ambulance services.
"We don't have enough vehicles, and that limits coverage," Mr Page said.
He added that there is no specific legislation that provides for ambulance services and there is an over-use of volunteers while the service is underfunded.
"The ambulance network is systematically under-resourced. The government needs to take direct responsibility for the ambulance service," he said.
A spokeswoman from the Ministry of Health said 100 new paramedics will be added to frontline emergency services over the next four years in a $28 million investment.
There are approximately 435 fire stations and 200 ambulance stations in New Zealand.