The Prime Minister is adamant the Government is doing enough to prevent recidivism amongst Maori.

The United Nations has voiced its concern regarding the over-representation of Maori in prisons and now a group of lawyers is taking the Department of Corrections to the Waitangi Tribunal.

John Key said the case has been brought by a former corrections officer and said the Government tried to get it struck out.

SEE ALSO: John Key speaks to Mike Hosking

He said the Government is turning every prison in New Zealand into a working prison.

"If you go out to Wiri, you don't just sit around all day. You actually get a skill in terms of a trade of some sort. Every prisoner that wants a drug or alcohol programme now gets that."

Key said the Government doesn't send people to prison, the courts do.

But a criminal justice watchdog says the Department of Corrections is not only unfair to Maori, it's costing other taxpayers as well.

Just Speak spokesperson Julia Whaipooti said the Waitangi Tribunal case will be an opportunity to improve figures, and save the Government money.

LISTEN ABOVE: Julia Whaipooti speaks to Mike Hosking

"What is wasting taxpayers money is the fact that is costs $100,000 a year to keep a prisoner in prison. So the claim would be that Corrections is wasting our money because they're not effectively addressing our prison population."

A lawyer says the Crown has an obligation to advance and protect the interests of Maori, and could be in trouble for not doing so.

Chen Palmer public law expert James Dunne said: "When you look at those figures, which do show that Maori are more likely to be arrested, more likely to be charged, more likely to be convicted, whatever the Crown is going in terms of criminal justice, it's not living up to it's obligations to Maori."

Dunne said it's going to be a big case and the tribunal will have to look into a big area of policies, not just individual cases but the functions of the justice system itself.

An urgent hearing will be held in June.