National's policy to reintroduce private management of prisons would cost more and could discourage the delivery of key rehabilitation programmes, Corrections Minister Phil Goff says.

National's law and order spokesman Simon Power reiterated at the weekend his party intends to allow private companies to tender for the management of some prisons if it becomes government.

The previous National government allowed private operator GEO to run the Auckland Central Remand Prison (ACRP) in the 1990s, but after five years Labour did not renew its contract.

Mr Goff today said Labour was philosophically opposed to private management of prisons, which necessitated the use of "coercive powers" over citizens.

Labour had the same view in regard to police, firefighters and the Defence Force.

But he also said in the case of the five-year ACRP experiment, private provision had proved more expensive.

He said in the last year of private management it cost $44,000 to keep a remand prisoner in ACRP, against $33,000 in a prison in the public sector.

"And because you tender it out to a specific institution, it does not do the really important but quite expensive things that the public sector will do like rehabilitation of sex offenders," Mr Goff said on Radio New Zealand.

But Mr Power questioned why, if private management was so expensive, the eventual operators of ACRP won the tender and the public prison service came last in that process.

Recent advice to ministers also said the public service should consider adopting some of the innovations the private managers of ACRP had introduced.

"Many of them have been because they were so successful," he said on Radio New Zealand.

They included 24-hour nursing care, better education and an excellent relationship with local iwi.

A previously released report into the prison found that private firm GEO managed to run it with a lower ratio of staff to prisoners and offered some programmes not available in the public system.