UPDATED 4.37pm The Police and Corrections Minister is blaming gang culture for an upsurge in reoffending by criminals, and staggering numbers of Māori in prison.
Latest figures show a marked jump in the prison population - it sits at around 9300, and over half of those inmates are Maori.
Another 500 inmates are expected in New Zealand prisons by the end of the year.
Judith Collins said around 40 percent of the prison population are gang members, or closely aligned to gangs.
Collins said if we want to deal with recidivism of a violent nature, we have to change that gang culture.
LISTEN ABOVE: Judith Collins speaks to Mike Hosking
But the Greens believe policy failure's why the prison population's going up.
Green MP David Clendon said there hasn't been enough investment in rehabilitation and reintegration.
"Out of a $1.2 billion operating budget, the Government's spending currently about $10 million on reintegration, and that is the major gap in our efforts to reduce offending and make out communities safe.
"There are more people in jail now than have ever been before, despite a diminishing crime rate. That suggests the policy settings are seriously out of step.
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In an effort to deal with the all-time high prisoner numbers, 130 extra beds could be created through double-bunking.
Corrections chief executive Ray Smith today admitted to the law and order select committee that double bunking has caused violence in the past, but he's confident they can manage it.
"As long as you design the facilities well and staff it well, double-bunking can be accommodated.
"So it's not ideal in some circumstances, but I think if you do it well, it's fine."