Inmates have made more than 120 serious complaints against Irish Prison Service staff since the beginning of last year.

Only eight were upheld or partly upheld.

There are six categories of complaints prisoners can make against staff under the Irish Prison Service's complaints system.

The most serious are ‘Category A’ – which are investigated by outsiders.

According to details released under the Freedom of Information Act, prisoners made 80 of these last year and 42 in the first seven months of this year.

There were 58 assault accusations made against staff and 17 allegations relating to sexual incidents.

Meanwhile, there were seven allegations of racial abuse.

There were a total of 33 allegations of mistreatment in jail.

The highest number was at the Midlands Prison, where there were 23 complaints against staff.

Of all the complaints made, only six were upheld and two were partly upheld.

Gabriel Keaveny said he believes the vast majority of the complaints against staff are “vexatious.”

“We believe that the statistics actually support our view,” he said. “And what happens in essence is that it makes our work very difficult indeed.”

“We welcome independent investigations; however, we would say that, where complaints of a vexatious nature are made, prison officers should be supported in the work they are doing by management of the prison service.”

The Irish Prison Service says all prisoners have the right to make a complaint at any time and all complaints are treated seriously.

Reporting from Eoghan Murphy