The United Nations Committee against Torture has branded so-called slopping out in some of Ireland's prisons degrading and inhuman treatment.
The Geneva-based international watchdog said it was deeply concerned and called on the Government to immediately eliminate the practice.
The UN also recommended that until all cells have in-cell sanitation, prisoners should be released to use toilet facilities at all times.
The body expressed concern at reports of continuing overcrowding in the State's jails and called for an independent system for dealing with prisoner complaints.
Executive director of the Irish Penal Reform Trust Liam Herrick said: 'The expert UN committee has made clear that an independent system for investigating complaints by prisoners is the most important protection against potential mistreatment of persons in detention.'
The committee said it was gravely concerned that 16 and 17-year-olds were being detained in Dublin's St Patrick's Institution, which it said was a medium-security prison that was custodial instead of a care facility for youngsters.
It recommended that the Government proceed without delay in the construction of the National Children Detention Facilities at Oberstown, Co Dublin.
The watchdog also raised concerns about violence amid prisoners, and said the Government should tackle contributing factors such as drugs, feuding gangs and a lack of activities.
Prison officers should also receive training on how to tackle inmate violence while Traveller intimidation must also be looked at.
Last week, the Inspector of Prisons, Judge Michael Reilly, highlighted a litany of concerns in the State's jails, including severe overcrowding, slopping out and broken windows.
He also criticised the detention of juveniles with adults in St Patrick's Institution and how deaths in custody are investigated.
