Keeping young people in cells is inappropriate and was only done for 700 children and teenagers in the last five years as a last resort, the police say.
RNZ News reported on Thursday a lack of suitable accommodation in youth justice facilities run by Child Youth and Family (CYF) had led to almost 700 children and teenagers being held in police cells in the last five years.
National Prevention Centre youth manager Inspector Ross Lienert said police had made several changes in how they dealt with youth offenders, especially when it came to holding them in custody.
Mr Lienert said police knew a prison cell was not the best place for a young person, but they also had a responsibility to stop people harming themselves or others in the community.
That sometimes meant a young person had to be held in a police cell for a short period of time, but they were closely monitored to ensure their wellbeing.
Two teenage boys spent a total of four nights last month in a police cell in Nelson because there was nowhere else for them to go.
One, a 15-year-old, was there for three nights over Easter.
CYF's general manager of high needs Nova Salomen said at the time that youth residences had a high turnover, and when beds were full social workers found alternative arrangements in the community.
The number of young people held in a cell dropped to 51 last year, which Social Development Minister Anne Tolley attributed to a joint action plan between CYF and the police.
She said changes included improved information-sharing between the two agencies, improved local transport arrangements and a better out-of-hours response.
Mrs Tolley said the government's focus on reducing and preventing crime and youth crime had led to fewer young people coming into the justice system.
CYF operates 146 youth justice beds in four centres around the country, but availability changes daily.