Inspectors have found the Corrections Department is locking up teenage prisoners for up to 23 hours a day in Mt Eden Prison, putting their lives at risk.
Prison inspections carried out by the Ombudsman have revealed about 70 teenagers are being held among adult prisoners and are allowed out of their cells for only about an hour a day.
The Ombudsman warned Corrections last year it needed to make changes but since then conditions for the teenagers have worsened.
When the Ombudsman's prison inspector went to Mt Eden in April last year there were 18- and 19-year-old prisoners being held in cells for 19 hours a day.
Since that April visit Corrections has closed Waikeria Prison's youth unit and the young prisoners on remand are now sent to Mt Eden.
The Ombudsman's annual report found Corrections had not set up a youth unit at Mt Eden, as it had been told to do, and teenagers were still locked up with adult inmates with little or no access to programmes or activities.
In June, there were 53 prisoners aged 18 and 19 at the prison and a further 18 younger than 18.
Young people in detention were extremely vulnerable and social isolation can be extremely distressing and even fatal, the report said.
NO COMMENT FROM MINISTER
Corrections Minister Sam Lotu-Iiga has declined to comment on the matter and Corrections would not make anyone available for an interview.
Corrections in a statement said it was strengthening the opportunities for youth at Mt Eden.
"We are actively working to increase the opportunity for young prisoners to participate in constructive activity while maintaining their safety, and the security of the site."
Corrections said it was also looking to appoint an officer that young people could to talk to about any concerns they have for their safety.
Green Party corrections spokesperson David Clendon said locking children in cells for 23 hours a day in an adult prison was like torture.
"It is normally only the most violent, the most dangerous prisoners who are kept in their cells for 23 out of 24 hours," Clendon said.
"Clearly, this is Corrections very poor attempt to make these young people safe by locking them away from other offenders, that's a completely unacceptable approach."
Labour Corrections spokesperson Kelvin Davis said he was worried the conditions will leave the young remand prisoners feeling their lives were worthless.
"Their time out of their cells has been reduced from some five hours a day down to one to two hours a day," Davis said.
"The big thing is when these young people emerge from prison, are they going to be in a better state of mind to assimilate and move back into the community or are they going to be in a worse position?
"Are they going to be more damaged and therefore probably likely to commit more harm and crime out in our communities?"
New Zealand First's youth affairs spokesman Darroch Ball said holding 16 and 17 year olds in an adult prison is a recipe for disaster.
"You talk about their mental health as well, they're having to keep them locked up for 23 hours a day.
"That's out of convenience for the Corrections Department, it's out of convenience for youth justice, it's not for the benefit of those youth.
"The Minister of Corrections clearly must know this is occurring, the Minister of Social Development clearly must know that this is occurring - they need be held to account.
"They need be questioned about why this is happening and what they're going to do about it."
A version of this story was first published on radionz.co.nz.