The Corrections Association of New Zealand (Canz) said a prison officer was assaulted in a "cowardly and unprovoked" attack at the Otago Correctional Facility on Monday. The attack left them requiring hospital treatment.
It was the second serious attack since April 15, when two officers were taken to hospital after allegedly being assaulted while a cell was being unlocked.
Also on June 9, two prisoners assaulted a staff member while leaving the exercise yard.
Force had to be used to restrain the two prisoners and the staff member was transported to hospital for treatment, Mr Miller said.
Data released to the Otago Daily Times showed from January last year until the date of the April attack, there were 42 cases where staff members required medical attention due to assaults.
A source, who asked to remain anonymous, said the latest assaults were linked to gangs at the prison and had left staff worried for their safety.
The source said management at the prison was not doing enough to keep staff safe.
Otago Corrections Facility general manager Dave Miller confirmed the two recent assaults.
In Monday’s attack, an officer was struck on the head by an inmate, and was transported to Dunedin Hospital, Mr Miller said.
The prisoners involved were relocated to the management unit and had been or were in the process of being charged with misconducts.
"Corrections officers come to work every day to keep New Zealanders safe and the assaults are unacceptable."
While the perpetrators were from the same gang, there was no evidence to suggest the assaults were linked, Mr Miller said.
"At present, there is not higher than usual gang tensions at Otago Corrections Facility, and this is monitored closely by our on-site staff and intelligence teams. Monitoring gang tensions is a standard part of our daily business.
"We are continuing to work with the unions to implement our Reducing Violence and Aggression Joint Action Plan and developing the next phase of this plan, called ‘Safer Prisons’, to ensure we are adapting and responsive to the current challenges and risks of the prison environment."
Canz secretary Mark Duncan said it was understood the assault on Monday was linked to gang activity.
"It is our understanding that the attacker was part of the ‘Crips’ gang and may be the result of an inter-gang conflict."
Mr Duncan said a nationwide increase in the prison population meant there was now a staffing crisis among Corrections.
He also said over the past years prisoners had become more violent and unpredictable.
"Our thoughts are with our colleague and their family as they recover from their injuries, after what can only be described as another cowardly and unprovoked attack on a staff member.
"Prisons are a dangerous work environment and OCF is no different."
He said the specific unit where the assaults occurred was initially assessed on the department’s prison tension assessment tool as "amber", which meant site management provided additional resources and introduced targeted plans to mitigate risk to staff and prisoners.
"We have been in contact with OCF’s general manager to find out further detail and he advised us that the unit was reassessed and was back to normal operational status."
Concerns about the safety of staff at the Otago Correctional Facility began stepping up in recent years as it emerged the proportion of high-security beds at the prison was increasing.
Last year Canz vice-president Paul Dennehy said the prison had morphed from a "green and pleasant" facility to a high-security jail.
