National is astounded the Government has given the go-ahead to the installation of under floor heating in four new prisons.

Corrections spokesman Simon Power says it is a disgrace, as is the fact the Government is refusing to reveal the cost of the luxury.

Mr Power believes the revelation will horrify taxpayers. He says not many law-abiding people can afford under floor heating in their homes and the public will not be expecting to pay for it for some of the country's worst criminals.

The prisons with under-floor heating are Northland, Auckland Women's, Spring Hill and Milton.