Prison Officers at two of the country's largest prisons are to begin work stoppages later this month in a dispute over staffing levels.
The Prison Offices Association (POA) served notice of industrial action on the Irish Prison Service today.
Prison officers at Clover Hill Prison are to stop work for one hour on two days later this month - Thursday 18 and Friday 19 September.
One-hour work-stoppages will then take place for two days the following week at Mountjoy jail.
Prisoners at the two prisons will remain locked in their cells for another hour after lunch as the industrial action takes place.
The POA has accused the prison service of breaching local agreements on staffing levels.
It says that management expects them to continue to provide full services with insufficient staff.
The association also claims staffing levels are often "dangerously low" at the prisons and that the Prison Service is in breach of health and safety agreements.
The Prison Service says it is disappointed by the decision which it claims is a breach of the Haddington Road agreement.