The prison officers union says the latest prison attack shows the need to bolster equipment and policies to deal with prisoners.
A prisoner at Auckland Prison was taken to hospital with serious injuries on Saturday morning after he was attacked by another prisoner armed with a makeshift weapon.
The Corrections Association understands the attacker was Graeme Burton, a double murderer.
Burton is serving a life sentence with a minimum non-parole period of 26 years for killing a Lower Hutt man last January while on parole.
Burton previously served 14 years in prison for murder after a fatal stabbing outside a Wellington nightclub in 1992.
Corrections Association says prison officers are not equipped to deal with prisoners like Burton and it is going to get worse if prisoner numbers increase.
