There were 320 assaults in Irish prisons last year.
Almost four out of every five involved prisoner-on-prisoner attacks.
There were 250 assaults involving inmates attacking other inmates in Irish jails in 2020.
The highest amount was in Cork prison, at 64, followed by 44 in Castlerea, and 29 in Midlands Prison in Portlaoise.
There were also 70 assaults by prisoners on staff - down from 123 in 2019, with the fall due to Covid restrictions in prisons.
Jim Mitchell, from the Prison Officers Association, says several members have suffered serious injuries over the years.
There were 120 cases of prison officers having to take time off work last year due to injuries they received on duty.
They missed an average of 52 days each.
The Irish Prison Service says any act of violence against a prison officer is unacceptable, and the necessary support is provided to victims.
