Police have slammed a photographer's "extremely dangerous" stunt after he was caught hanging out the boot of a moving car during a photoshoot on Auckland's Harbour Bridge.

On Sunday around 5.30pm a white hatchback was seen driving up the bridge with the boot wide open as a photographer had his body hanging out the back while holding camera equipment.

Behind the hatchback was an Audi R8, with both cars driving at speeds of up to 80km/h heading northbound.

According to a witness, who wishes to remain anonymous, the two cars, believed to be from the same party, were seen manoeuvring between lanes before getting off at the nearest off-ramp.

The witness told the Herald he saw the photographer hanging out the boot from as far back as the Victoria Park tunnel.

"We saw the car behind tailgating the front car. Then as we got closer we saw the boot of the hatchback open while they were in the tunnel and a man hanging out of it close to the road with a camera taking pictures of the car behind.

"We are certain they were together as they kept changing lanes at the same time.

"When they got to the bridge they started taking photos again as they went up the bridge.

"That's when we took the photo. After the bridge they got off at the first exit and got in the lane to turn around. We suspect they were going back for more bridge photos."

Police confirmed they received reports of the incident, slamming the stunt as "extremely dangerous" and "illegal".

A police spokesperson told the Herald someone could have been seriously injured.

"Police received a report of this incident around 5.40pm yesterday, and are making inquiries to identify those involved.

"The behaviour reported appears to be illegal and is extremely dangerous.

"This activity could have resulted in a serious accident and police urge those involved to think about other road users when partaking in such behaviour - this is not worth the serious injuries or worse, that could easily have occurred."

Police ask anyone who may have information about this incident to contact them on 09 481 0782 or anonymously via Crimestoppers on 0800 555 111, quoting file number 190729/5465.