The Government says a new multimillion-dollar prison for South Auckland may not be needed because the number of prisoners is expected to fall dramatically.

A Ministry of Justice forecast says the prison population is expected to drop 6.2 per cent by 2021.

Over the past decade, it grew 45.6 per cent.

The predicted drop is being attributed to several factors, including a fall in recorded crime, and greater use of police diversion for low-level offences.


Prime Minister John Key said it was possible that the 1060-prisoner facility planned for Wiri, in South Auckland, may not be needed.

"We're obviously pleased about the falling numbers of prison inmates.

"It may be that Wiri will still be built on the basis that some of the older prisons may be retired. It's not clear- cut."

The cost of the prison is subject to a competitive tender, but the Green Party has claimed it will cost at least $300 million.

Alcohol and drug counsellor Roger Brooking, a critic of the Corrections Department, said the money would be better used for more treatment facilities.

"In particular it could be used to provide more treatment for alcohol and drug abuse - one of the main drivers of crime."

The prison population was 8708 in June; the forecast for June 2021 is 8165.

The imprisonment rate per 100,000 people is projected to fall from 198 this June to 170 by June 2021.


Construction of the prison at Wiri is due to start in the second half of next year and is expected to open in April 2015.

New Zealand now has accommodation for 9560 prison inmates, and the number of people in jails is 8564.

Wiri is intended to be a public-private partnership, and three consortiums are shortlisted for thecontract.

The winner is expected to be announced early next year.