The Independent Police Conduct Authority says two experienced police officers breached pursuit policy in separate police chases last year that left a driver dead and another seriously injured.
The IPCA says one officer chased two street racers near Palmerston North in May last year without using his siren and did not follow procedure.
The driver of one of the cars, Jason Downes, crashed and was killed instantly.
The officer said he wasn't pursuing but the Authority believes his actions amounted to just that.
The IPCA has also ruled policy was breached in Lower Hutt last November by a second officer who failed to activate his siren and lights while chasing a driver at 120km/h in an 80km/h zone.
The driver, Benjamin Eden, received serious head injuries.
The IPCA says neither officer broke the law, but both need remedial training in pursuit policy.
The police say they accept the findings and have implemented the recommended training.