The Assistant Commissioner for Road Policing says police chases last a matter of seconds and are called off promptly if considered dangerous.
Four men, aged 18 to 20, died over the weekend after their car crashed in Auckland following a police pursuit early Saturday morning.
The Independent Police Conduct Authority is investigating the chase, which police said was twice abandoned when speeds got too high.
In 2007, Kellie Tremayne's nephew Jamie McElrae was a passenger in a car that failed to stop for the police. The car subsequently crashed and the 17-year-old was thrown from the vehicle. He died the following day.
Ms Tremayne told Radio New Zealand's Morning Report programme there were several inconsistencies in the police report given to her family, including how quickly they called off the chase.
She said she finds it "too unreal" that most police pursuits are said to have been called off moments or seconds before a crash.
Ms Tremayne said that in media reports on more than 20 pursuits where someone subsequently died, police said in all but one case that they had ended the chase minutes before the fatality.
"Every single time it seems they just called the police chase off ... I think there's something really suspicious just in that alone."
Assistant Commissioner for Road Policing Dave Cliff says there's a perception that pursuits last a long time, but this is not the case.
"They're very quick. Our people are assessing the risk all the time. If it's dangerous they're required to pull out, pull over to the side of the road, turn off the lights and siren and stop and call the pursuit off."
He says there are tight procedures on pursuits which are being constantly reviewed.
Road safety campaigner Clive Matthew-Wilson says the police should follow the example of other jurisdictions around the world that ban chases, and where officers instead keep a distance and call in a police helicopter.
In a statement, Police Minister Anne Tolley backed officers and said police must always act to protect the public from dangerous drivers.
"Any deaths on the road are tragic, and I hope these recent terrible events will act as a deterrent to any speeding drivers, or drink-drivers, and stop anyone thinking of getting into a car with someone who has been drinking. Drivers should never try to flee from the police."
Ms Tolley said police learn from every incident and they have her backing to keep communities safe.