Hundreds of boy racers have pelted police patrol cars with missiles in Rotorua, damaging two of the cars.
Thirty-one arrests were made after the crowd of 900 got together to demonstrate against legislation that would permit the confiscation of cars used in illegal street racing. The police were also verbally abused.
Officers say the gathering was originally touted as a peaceful 'park-up', but got out of hand when the boy racers moved south of Rotorua and started drag-racing and skidding. About 230 cars, some from as far afield as Auckland and Napier, were involved.
Senior Sergeant Denton Grimes of the Rotorua police says the incident is a breach of trust, as the organisers of the gathering had been warned that there would be zero tolerance of unlawful behaviour.
The 31 were charged with a range of offences, including breach of liquor ban, unpaid fines, driving while disqualified and "sustained loss of traction".