A Wellington man says his neck was broken by police as he was being evicted from a party.
The Independent Police Conduct Authority has confirmed it has received a complaint from Jakob Christie.
The 19-year-old says he was hit on the back of the neck by a police baton as he walked quietly out of a flat in the suburb of Khandallah with his hands raised above his head last Friday.
"I put my hands in the air as if to say 'I'm not resisting, don't hit me'. I'm almost out the door and then I got hit in the back of the neck by a baton."
He is now in a neck brace and may need an operation on a fractured vertebrae.
Mr Christie told Checkpoint he was not one of the troublemakers at the party and says the blow was cowardly.
He believes the officer involved should be charged with assault.
Allegation to be 'thoroughly' investigated
Wellington police say the complaint will be investigated thoroughly and could take months to complete.
Police commander Inspector Pete Cowan says he was told of the incident by a concerned parent and is horrified at the claim.
Inspector Cowan told Checkpoint he advised that a complaint be made to the IPCA and says Wellington police will conduct its own investigation.
"These are very serious allegations - I can't stress that strongly enough - and the investigation will be thorough, I can guarantee that. Because at the end of the day, these actions are not only inappropriate, but potentially unlawful."
Mr Cowan says up to 80 witnesses may have to be interviewed.
IPCA spokesman Bernard Steeds says the complaint was received on Monday and it is not possible to say when it will be resolved.