Three officers at Auckland Prison have been suspended and charged after inmates allegedly stabbed a corrections officer in May.
The guard was wearing a stab-resistant vest at the time and was taken to hospital for treatment.
Three inmates allegedly involved in the attack were also hospitalised that night, and now three Corrections officers have been charged due to their use of excessive force in the incident.
The three prisoners appeared in court last Tuesday jointly charged with wounding with intent to cause grievous bodily harm and aggravated assault. All three have been suspended.
One of the officers will be charged with attempting to pervert the course of justice, another with assault with intent to injure, and the third with causing grievous bodily harm with reckless disregard.
Police say the officers were investigated due to injuries received by the prisoners during the incident and after "concerns were raised by Corrections".
Auckland Prison director Andy Langley said "standard procedures in the event of a use of force were allegedly not followed", which was passed on to police.
"Corrections has a zero tolerance to violence policy. No assault or violent behaviour by a prisoner, or a staff member, is acceptable," he said.
"Anyone who takes part in this kind of behaviour can expect to be prosecuted."
The trio are due to appear in the North Shore District Court on Friday morning.
It's believed the original stabbing was gang-related, with Corrections saying the prisoners used "improvised weapons".
An operational review is now underway and Mr Langley said changes have been made to the management of the wing where the incident took place.
At the time, Corrections Association president Alan Whitley said officers need easier access to pepper-spray in the prison's wings.
Sprays are available, but it isn't easy for guards to get their hands on it quickly.