UPDATED 4.00PM By 2017 our prisons are expected to bulge with about 10,000 inmates.

Half of those will be Maori.

That's prompted former probation officer Tom Hemopo to front the Waitangi Tribunal this morning, saying the disparity between Maori offending and the Maori population is unacceptable.

A 2009 Corrections report found 77 per cent of Maori offenders were reconvicted after five years out of prison.

Mr Hemopo told the Tribunal there's no long-term commitment by the Crown to get those numbers down.

He said the Maori Focus Units are always praised, but make little impact.

"I've found that the Maori Focus Units only take around 250 men a year, so it's hard to see how they can help the over 4000 Maori men and women in prison."

He told today's hearing, rehabilitation programmes are treated as a privilege in our prisons, and that creates inequality.

And he said there is no-one to guide offenders through the transition from prison to probation.

His lawyer Peter Andrew said there is no strategy, target or commitment from the Department of Corrections to tackle the issue and that goes against Treaty of Waitangi principals.

"At all stages of our criminal justice system, Maori are over-represented, whether it be incarceration rates, whether it be youth offenders, or prisoners on remand."

Barrister Peter Andrew said the disparity between the number of Maori people in prisons and the Maori population has gone on too long.

He said the solution is to completely re-think how corrections works and change how it operates in society.

The Crown says the matter would be better dealt with in a kaupapa inquiry relating to justice generally.

Dr Tracy McIntosh gave evidence at the hearing and said about 20,000 children have a parent in prison and a high proportion of those are Maori.

She said it's one of the key reasons Maori are over-represented in our prisons as ties with whanau are continually broken.

"The inter-generational reach of the prison is much more marked when women are imprisoned. The impact on children is immediate and devastating and in too many cases we'll see them put into state care themselves."