Prisoners will each cost the taxpayer more than $92,000 this year, 63 per cent more than they did in 2001.
National MP Simon Power is astounded at the increase, which he says is driven by the construction of flash new prisons with flat-screen TVs and underfloor heating.
According to figures supplied to Parliament's law and order select committee by the Corrections Department, the cost per inmate is projected to climb to $253 a day - or $92,345 a year - in the 2007-08 year.
In 2001, it was $155 a day, or $56,575 a year.
The new cost is "higher than the cost of a room at many top hotels with breakfast thrown in", Mr Power said.
Corrections said the increases had been driven by the cost of building prisons in Northland, Otago, Auckland Region Women's Prison and Spring Hill Prison in Waikato.
However, Mr Power said the real reason was "the shoddy and cavalier way" in which the building programme was handled.
The cost of building the four prisons ballooned from $400 million signed off in 2002, to $890 million - a blowout of $490 million.
A report by the State Services Commission last year slated Corrections for mishandling a key aspect of the contracting method, known as a collaborative working arrangement.
Rather than contractors tendering individual prices, such agreements require all parties - including designers, builders and clients - to agree on an overall cost to help minimise risk.
However, indicative costs were not established till years after construction began.
"And, at the same time minister Damien O'Connor was promising the prisons were `not gold-plated', they were spending $11 million on landscaping and purchasing flat-screen TVs for six prisons, as well as PlayStations and Xboxes and installing underfloor heating," Mr Power said.
"There is no doubt this Government's slack use of taxpayers' money has contributed greatly to the huge cost of keeping prisoners."
Mr O'Connor was not available to comment yesterday.
A Corrections spokeswoman said the increase in the cost per prisoner per day came about because of the "operating cost implications of significant capital investment" in recent years.
"This investment was needed because a forecast rise in prisoner numbers meant Corrections had to build additional prison facilities to increase capacity."
The number of inmates hit a record high of 8076 in May, forcing authorities to accommodate some prisoners in police stations and court cells.
As well as the building of the new prisons - which will add more than 1600 new beds - a further 773 beds have been approved for construction at the existing Rimutaka, Tongariro/Rangipo, Wanganui and Christchurch prisons, the spokeswoman said.
"Without the increased capital costs, the cost per prisoner per day would have only increased marginally due to inflation and an increase in the salaries of Corrections Officers last year."
- The Dominion Post