The detention of hundreds of youths in unsuitable police cells - some without adequate food or access to a shower - raises "significant human rights issues," a new report says.

In one case, a young woman with medical and mental health problems reported being held for five nights, without medical care or suitable food for several days.

Two Upper Hutt teens were recently detained for 36 hours, strip-searched and one was forced to express breast milk into a sink.

The Independent Police Conduct Authority (IPCA), the Children's Commissioner and the Human Rights Commission conducted a review on the treatment of young people in custody, and found it was variable because of issues including the condition of the cells, police training and levels of understanding about best practice.

It made 24 recommendations, including improving data collection and reporting requirements, and introducing further training for those involved in the care of detained youths.

IPCA chair judge Sir David Carruthers said keeping young people in custody was sometimes necessary, but there were more constructive responses to their offending.

"We need to focus on preventing and reducing youth offending as well as identifying alternatives to police detention."

Carruthers said he hoped the report would help reduce the number of young people held in police cells, and make sure appropriate attention was paid to their needs and rights.

"Improvements can and should be made," he said.

The report showed 740 youths were remanded in police custody for more than 24 hours in 2006, with some being locked up for three to six days.

In 2009, the number went down to 76, but then went back up to 131 in 2010, resulting in criticism from both international and domestic groups, including the United Nations Committee on the Rights of the Child.

Last year, 213 young people were remanded in custody for an average of 1.9 days. Of those, 148 were initially arrested on Friday, Saturday or Sunday and were generally held until Monday.

The report said most youths were held because of no suitable alternatives, no availability to transport, or because of the day of the week they were arrested.

Police cells were never intended for the detention of young people, and there were practices which violated, or were at risk of violating, accepted human rights standards, it said.

Some youths had cell lights on 24 hours a day to allow suicide monitoring, a lack of ventilation and natural light, inadequate food, or no access to shower facilities.

Young people also reported being treated as adults, with the use of force, or feeling discriminated against.

Children's Commissioner Dr Russell Wills said when a young person was arrested, "it's an opportunity for them to turn their life around".

"If that doesn't happen, or worse, if the young person is mistreated or doesn't know their rights, there are other consequences that follow and they are more likely to reoffend."

Police's Assistant Commissioner Nick Perry said policing children and young people was where prevention of crime starts, and police were "very mindful" of the need to get it right.

He said a youth policing strategy had just been released. It sets out how police will increase the protection and safety of youths, and reduce their presence in the criminal justice system.

"Policing of children and young people does present unique challenges. We recognise that and our strategy outlines ways that we will ensure we have better training, decision making and auditing processes to make sure we are complying with our own policies and procedures as well as international conventions that New Zealand is part of," he said.

The review found there was a lack of information available to monitor and asses how police were exercising their discretion when arresting, charging or remanding a youth in custody.

Police reports sent out to the districts should be improved as they were insufficient to asses police compliance or identified trends of non-compliance.

It was essential for young people to understand their rights and have access to support while in custody since some youths reported not always being able to contact a lawyer, the report said.

Alternatives to police custody should also be looked at, including the supported bail programme, an initiative aimed at assisting young people who would otherwise be remanded in custody while on bail.

The report recommendations also include:

- Child, Youth and Family undertake a review of, and develop a coherent strategy around, the provisions of suitable facilities for the safe detention of young people.

- Police develop a comprehensive and nationally consistent youth-specific training programme for all front line staff, custodial staff and supervisors.

- Police and Child, Youth and Family develop an information-sharing protocol especially with regard to youth custody issues.

- When building any new police station, or making alterations to existing ones, police give consideration to how the needs of young people in custody may be better planned for and accommodated.

- Police work with Child, Youth and Family and the Ministry of Justice to minimise the need to transport young people to and from court.

- Police and Child, Youth and Family make arrangements for police to make a notification or "report of concern" each time a young person spends time in police custody.

- © Fairfax NZ News