The Green Party wants more drug and alcohol rehabilitation in prisons to reduce the high rate of Maori being locked up.
A United Nations report into New Zealand's race relations shows Maori are still over-represented in all stages of the justice system, and it wants data from the Government to show how it's making progress.
Maori make up about half of the roughly 8000 prisoners in the country.
Green party spokesperson for Justice David Clendon says that statistic is partly due to racial bias in arrest rates and other stages in the justice system.
And he says too much money is going in to locking people up instead of rehabilitating them to stop re-offending.
Mr Clendon says the solutions are obvious, including proper drug and alcohol treatment, investment in mental health services and practical support to aid reintegration post-release.