New Children's Commissioner Judge Andrew Becroft has launched a campaign to persuade Cabinet ministers to raise the upper age limit for the Youth Court from 17 to 18.
Becroft, who has just started a short two-year term as commissioner after 15 years heading the Youth Court, has written to all ministers and plans to meet with all of them to get the age raised.
The Government has already introduced a bill to implement an expert panel's proposal to raise the age limit for state care of young people in need of care and protection from 17 to 18, but ministers are believed to be divided over whether to raise the age limit for youth justice.
Helen Clark's Labour Government introduced a bill to raise the age for leaving both state care and youth justice to 18 in 2008 but the bill was dropped by John Key's incoming National Government at the end of that year.
Justice Minister Amy Adams said last year that she had asked officials to look again at the issue, but her predecessor Judith Collins - now back in Cabinet as Police and Corrections Minister - was firmly against it.
Judge Becroft said it would be "illogical" to let young people stay in state care until they turned 18 while pushing them out of the youth justice system at 17, because 70 per cent of young offenders had been in the care and protection system.
"So we would be having in the adult District Court people who are still only children in the care and protection system. It's going to be a complete organisational shambles," he said.
He said there was a misperception that the youth justice system was "soft".
"We have a person who is 14 who committed two serious rapes in Porirua and was sentenced to six and a half years in adult prison," he said. "We are transferring 20 or 30 young people a year to the adult court."
But he said the youth justice system recognised that young people's brains were not yet fully developed, and tried to steer them on to a better path to keep them out of the criminal justice system.
He said raising the youth justice age was one of three priorities for his term as commissioner, along with monitoring the creation of a new ministry for vulnerable children and engaging with iwi and hapu to help with Maori youth, who made up 61 per cent of children in state care and 64 per cent of youth justice offenders -- up from 42 per cent eight years ago.
"The law directed that [engagement with iwi] pretty clearly in 1989," he said.
"We haven't delivered on it, both for the reason that Government agencies didn't work hard enough to build capacity and resources, and neither did hapu and iwi prioritise that work.
"The challenge is there for hapu and iwi. Tuhoe are doing it, and I think that's a good model."