Department of Corrections figures show attacks in the country's prisons have almost quadrupled over the past five years to reach 75, including 11 serious assaults, in 2008/2009, The Press reported.
Rimutaka Prison contributed 15 of those attacks including three which were deemed serious.
Corrections executive services manager Kelley Reeve said an assault could mean anything from a push to serious violence.
Corrections Association President Beven Hanlon disputed the figures, saying the number was likely to be about 700 a year.
A report by The Dominion Post last year also cast doubt on the numbers. When, in July, Corrections announced the introduction of stab-proof vests, batons, spit hoods and pepper spray it said assaults on guards had risen to an average of one per day.
Mr Reeve said assaults at prisons in Wellington and Christchurch were often committed by Aucklanders seeking to be sent to the country's only maximum security prison at Paremoremo.
"If you want to go to Auckland to be close to family, you make yourself maximum security, and you do that by assaulting guards."
Howard League for Penal Reform manager Kathy Dunstall told The Press the prison system had become more repressive in recent years with overcrowding, extended lockdowns, shortened visits and 70 percent of parole applications being declined.
"Frustration levels rise and people lose their rag quicker."
In July a Rimutaka Prison guard suffered multiple skull fractures and lost an eye after an inmate attacked him with a broom.
At the time Corrections said that despite an increasing prison population, since 1996 serious assaults on staff had decreased by 90 percent.
