Firefighters on route to emergency callouts have been told by their union to slow down or risk police prosecution.
Serious concerns have been raised around the use of J-rated tyres which have been fitted to fire engines and are only rated for a maximum speed of 100km/h, according to the New Zealand Professional Firefighters Union.
This is despite fire engines being allowed to travel at up to 105km/h under Fire and Emergency NZ's normal emergency response policies.
After receiving advice from police, the union now says drivers using fire trucks with J-rated tyres risk prosecution if they exceed the 100km/h safety limitation.
The situation has sparked warnings that people could die if firefighting personnel are delayed during emergency responses.
However, FENZ says the J-rated tyres are safe and are working with police to get further clarification around the issue.
The union's Auckland local secretary, John Waldow, said J-rated tyres were cheaper than the factory fitted M-rated tyres which were rated for speeds up to 130km/h.
He warned that using the cheaper tyres would result in delayed arrivals to emergencies and "any delay in the response of fire appliances or emergency vehicles could ultimately lead to a loss of life".
However, Region 1 fire region manager Kerry Gregory said the difference between 100km/h and 105km/h wasn't significant when travelling to emergency jobs.
"Particularly in the urban areas in which these tyres are used where speeds of 100km/h are not sustained for significant periods of time".
The union said its recommendations to slow down followed advice from a police officer in the Police Commercial Safety Team.
The officer's written advice said firefighters using fire trucks fitted with J-rated tyres should be aware of the vehicle limitations and there would be consequences for drivers who exceeded the tyres' maximum speed rating.
"Simply put, if an Appliance has "J" rated tyres then the driver has a responsibility to drive below 100km/h regardless of the circumstances.
"One hundred km/h is the maximum speed for a "J" speed rated tyre and this speed should not be exceeded loaded or unloaded," the officer said.
Despite the officer's advice and the union's recommendations, Gregory said FENZ had received advice from the manufacturers who said the tyres were safe.
"If there is a legal compliance issue created by our use of these tyres we will cease using them.
"In the meantime, as previously stated, I have instructed our personnel there are no circumstances in which I expect our appliances to be driven at speeds greater than 100km/h should drivers feel unsure about safety," Gregory said.
A police spokesperson told the Herald safety was their number one concern, for emergency service and commercial vehicles on the roads.
"It is especially important that our emergency services response vehicles are safe, as when they respond to incidents they are often travelling at high speeds.
"We can confirm that a view was sought from a member of Police, however, this was not a legal opinion.
Police were now in talks with FENZ on this matter, the spokesperson said.