Corrections Minister Kelvin Davis is aware that double-bunking in prison cells at Waikeria prison does not meet international standards, but says they will still be safe.
"At present we're not meeting international standards," he said.
"We'd prefer not to double-bunk any cells whatsoever, but we've got this plan in place now. The cells are purpose built for double-bunking in that they are bigger, and so we think that will maintain prisoners safety and staff safety."
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On Tuesday the Government announced it would scrap plans for a 1500 to 2000 bed prison in Waikato, and would instead install a new 500-bed unit and 100-bed mental health facility at Waikeria in rural Waikato.
The decision was made because the Government says mega-prisons don't work, but it will need to decrease the prison muster or find new beds if it is to avoid further overcrowding.
Mr Davis said he talked with Corrections officials about the plan for the double-bunked cells at Waikeria, which measure 9m2 even though the European Committee for Prevention of Torture (CPT) states that such cells should measure 10m2.
Mr Davis said the Government made a financial decision to have double-bunking at Waikeria, rather than something it wanted to do.
"It's more budgetary. We don't want to double-bunk. We don't want to build prisons in the first place, but, you know, that's where we've landed."
Waikeria will also see a new 100 bed mental health unit, providing treatment for prisoners with mental health diagnoses.
"It will be really the first of its kind at this level of treatment," Mr Davis said.
"There's some extreme mental health cases that Corrections have to deal with."
The Waikeria prison site was chosen because of its central location - close to the Bay of Plenty, Taranaki and Waikato.