A fourth cop from one Auckland police district has been stood down over assault allegations, prompting calls for an inquiry into violence within the force.

The constable allegedly attacked members of the public while on duty and was suspended after colleagues approached Waitemata police bosses. He has not been charged.

Police management have dismissed suggestions of a violent culture within their ranks but are reminding other staff in the district of how they should behave.

In May the Herald on Sunday revealed an officer, whose name and rank are protected by a suppression order, appeared in the North Shore District Court charged with assaulting five prisoners. One had a testicle surgically removed as a result of the alleged incident.

Last month constables Gareth Needham and Alan Douglas appeared in the Waitakere District Court charged with assaulting 18-year-old Josh Hart.

Waitemata district commander Superintendent Bill Searle refused to comment on the previous cases. But this week he broke his silence, saying he was "very concerned" about the situation.

"I can't comment on any cases that are under way but I can assure you, and the public, if we do have any other allegations of assault we will take firm and appropriate action," he said.

The accused officers are being investigated by the district professional standards unit and the Independent Police Complaints Authority.

Council for Civil Liberties chairman Michael Bott said he wanted a major inquiry.

"In my mind it would be appropriate for an independent body to investigate what's going on out there. You should be concerned when those who are charged with protecting New Zealanders start beating them up," he said.

Bott said he hadn't seen "such a concentration" of violence allegations "in such close proximity for a very long time".

Howard League for Penal Reform spokesman Nigel Hampton QC said the allegations were more indicative of management flaws than a culture of violence.

"Historically, this has happened in other areas ... police going their own ways came to regard themselves as above the law [and were] not curbed by leadership.

"[This] sounds like a similar absence of leadership, allowing such practices to grow and become the norm."

Searle did not accept there was a violent culture in his district and rejected claims of leadership or management issues.

"The fact that these cases came to our notice from other police indicates an intolerance from staff to inappropriate behaviour. I have every confidence in my area commanders."

Police National Headquarters human resources manager Wayne Annan said the allegations were "unacceptable and disappointing".

"Sometimes this [job] does require forceful intervention but officers are selected and trained to recognise the difference between acceptable use of force and assault.

"The small number of staff who face criminal charges ... should not detract from the outstanding work done by police."

Searle will hold individual meetings with every officer in his area. He has also emailed staff to tell them "unprofessional or unethical behaviour will not be tolerated".

He has also ordered all staff to attend a training course reinforcing standards, values and professionalism.

"As the district commander I can reassure the public that the huge majority of police act appropriately," he said.

Police Minister Judith Collins and Commissioner Howard Broad refused to comment.

Fourteen police officers were charged with assault last year, up from five in 2008.

Named and shamed:
* Officers Patrick Garty and Wiremu Bowers Rakatau were found guilty of punching and kicking a group of students while off-duty last year. The pair have indicated they will apply for a discharge without conviction.

* In March a High Court judge found Whakatane police subjected Rawiri Falwasser to an excessive abuse of power over seven hours in a cell.

* In 2003 police officer Alexander Grant received 16 months in prison after he assaulted a handcuffed man in the back of patrol car.