A police officer chasing an armed robber on a forestry road was justified in shooting at him 14 times as the robber reversed at him, the watchdog has ruled.

The Independent Police Conduct Authority's (IPCA) report into the shooting, released Tuesday, said the incident started when a man wearing a balaclava and armed with a tyre iron robbed a shop on the outskirts of Rotorua.

Police spotted him on a rural road 20 minutes later, but abandoned the chase due to risks to the public.

A short time later the robber rammed a police car and took off. He was eventually found driving down a dead-end forestry road.

Instead of stopping he turned around and rammed the police car and sped off.

He then stopped and reversed towards the police officer. The officer fired his pistol 14 times.

Bay of Plenty District Commander Superintendent Will Loughrin said the officer fired in self-defence and feared for his safety.

"This response escalated extremely quickly when the offender began using his vehicle as a weapon and was showing intent to cause significant harm or injury to my staff."

He said the shooting allowed the officer to get himself to safety and put an end to the dangerous situation.

"Police officers go to work every day to keep the public safe, but it is also important that they themselves can be safe. We want them to be able to go home to their loved ones at the end of each shift."

The robber was uninjured.