The union for prison officers is calling for guards to be armed with tasers and pepper spray following a "savage" attack at an Upper Hutt jail.
An officer is being treated in hospital for serious head injuries after a group of prisoners set upon another inmate and before he intervened at Rimutaka Prison near Wellington on Friday.
The low-security inmate is being treated by the prison's health centre.
Corrections Association president Beven Hanlon says the officer was viciously attacked by five inmates when he went to investigate.
Mr Hanlon told Radio New Zealand's Checkpoint programme on Friday the man was ill-equipped to deal with the situation.
"He was wearing his blue cotton uniform. That's what every Corrections officer wears - whether you're in a maxi unit or a minimum unit. We don't have pepper spray, we don't have batons, we don't have spit hoods and we don't have stab vests.
"The reality is, those things are locked away and the only time we ever hear about them is when one of us gets attacked and the department or the minister come out and say, 'These things are available' - well, really they're not."
Beven Hanlon says the injured officer is in an induced coma on Friday.
The Corrections Department has praised the officer and other staff for their efforts. Chief executive Ray Smith says the inmate was the victim of a spontaneous savage assault and staff did an excellent job by quickly bringing the situation under control.
Mr Smith told Checkpoint it is too early to say how serious the officer's injuries are.
"Other Corrections officers have been involved in this situation too and they did bring order, but we've got one very seriously hurt man."
Ray Smith says police are investigating and charges are likely. He says the incident was limited to one unit and the public's safety was never at risk.