A Serco staff member at Mt Eden prison has been suspended after being caught fighting an inmate.
Footage of the incident was discovered as part of a review into the prison being carried out after allegations of fight clubs between inmates and drug smuggling.
A spokeswoman for Serco, a private British company that was contracted to operate the prison, confirmed an officer had been suspended, pending a disciplinary hearing.
"The safety and security of staff, prisoners and visitors in Mt Eden Corrections Facility is paramount and we have zero tolerance for violence."
The Corrections Department has taken control of the Mt Eden Corrections Facility, which was being operated by private company Serco, following allegations of fight clubs and drug smuggling.
The Prison Inspectorate and the Ombudsman is carrying out a review of the prison after the allegations, and it was during this that footage of the incident involving the now suspended officer came to light.
A spokeswoman for Corrections Minister Peseta Sam Lotu-Iiga said in a statement that he was "aware of a number of allegations" involving the prison.
"The minister has previously expressed his concern about the allegations and awaits the outcome of the chief inspectorate's review."
Labour leader Andrew Little said the revelation was not surprising, as a picture was emerging that showed the prison operation was dysfunctional.
"It does look like there is something systemic there, in terms of the management of it, and it can't go on, and for the sake of public confidence it has to change.
"All this stuff is coming to light because of other people...as opposed to from the record-keeping by the prison itself. There is a question about how honest they are being in their reporting.
"There seems to me a real question as to whether proper accountability is being maintained, and therefore whether the contract between Corrections and Serco is adequate."