Youth prisons aren't working and the government needs to find new ways to decrease the prison population, a prominent Māori leader says.

An investigation is underway into how seven boys managed to overpower staff at the Korowai Manaaki Youth Justice Residence in Auckland, stole keys to the facility, and climbed onto the roof.

They were coaxed down by police and staff.

The escapade comes after the government announced plans to spend around $1 billion increasing the capacity of prisons.

Dame Tariana Turia, a former co-leader of the Māori Party, maintains that locking young people up together only leads to more offending later.

"It's very clear that when you put a lot of people together, they learn a lot from one another and clearly it's not positive or constructive," she said.

Dame Tariana insists the money would be better spent solving the issues confronting the families of youth criminals.

"The fact is, a billion dollars of taxpayer's money would buy a huge amount of rehabilitation for inmates and their families."

"I don't understand it."

New Zealand First youth affairs spokesman Darroch Ball yesterday calimed that young criminals are actually running the facility, and that over the past year, there have been between 680-700 security incidents.

A Department of Corrections Report released this week revealed that in the 2015/16 year just under 20 staff were seriously assaulted by inmates while on the job, and more than 450 minor and non-injury assaults were also reported.

In 2014/15 there were less than 10 assaults on staff classed as serious and just under 400 minor or non-injury incidents were recorded.