Child, Youth and Family deputy chief executive Ray Smith says the service is working to ensure fewer young people spend nights in police cells.
Lawyers and law agencies say that because of recent law changes, there are not enough beds at youth justice facilities.
In one case, a 14-year-old boy spent four nights in a cell because there was no residential bed for him.
Since October this year, the Youth Court has been authorised to send 12- and 13-year-olds to youth residences and maximum terms for all youth offenders have been doubled to six months.
Mr Smith told Nine to Noon that CYF got it wrong in that case and concedes other young people have spent more than one night in police cells in recent months but says that is about to be fixed.
"We've got a lot of capacity, including 12 supervised group homes which provide another 60 beds which we're just opening at the moment. I think we're in a good place - we've got a little blip here and we just need to tidy our act up."
Mr Smith says law changes are not to blame.
Auckland lawyer Helen Bowen says the 14-year-old client, who is a state ward, was arrested in November and kept in a police cell for four days because there were no beds available in suitable facilities.
Ms Bowen told Nine to Noon the number of beds had been increasing, but in the past couple of months the situation has deteriorated and there appears to be a nationwide shortage.
John Hancock from Community Service Youth Law says law changes may be responsible for the shortage of beds, as 15 young offenders have been handed the new maximum six-month residential sentence.
