Labour says the Government must end its prison "privatisation experiment" after a court revealed fight clubs may have been a weekly occurrence at Mount Eden prison, along with other serious issues.
Private prison operator Serco in February called for a judicial review into the chief prison inspector's draft report on organised fighting among inmates and access to contraband at the jail.
But a High Court this week found the report was fair and "without error" in concluding there may have been weekly "fight clubs" at the jail, animals may have gotten into food given to inmates and some prisoners were left waiting long periods without calls to lawyers.
Labour's corrections spokesperson Kelvin Davis said those findings showed there was no place for private prison operators in New Zealand.
"The Minister [Judith Collins] was wrong and needs to rule out Mount Eden being re-privatised," he said.
"The Minister of Corrections must end the privatisation experiment immediately."
Ms Collins declined to comment on the call by Mr Davis.
Corrections Department chief Ray Smith said he would consult with the Ombudsman before releasing the long-awaited report and would not comment further on details.
Serco took over the management of the Mount Eden remand prison in 2011, after winning a $300 million, 10-year contract.
The discovery of fighting footage uploaded to the YouTube streaming video website triggered an investigation last July into organised "fight clubs" at the prison, and came at a time when Serco's contract was up for review.
The Government stepped in to run the prison last July and didn't renew Serco's contract in December.
Mr Smith said the prison was still in transition to full Corrections staffing.