UP to 50 prisoners a day are released early from prison to make way for new arrivals, the Department of Justice has said.
Department officials said prison policy and operations were dominated by a "tyranny of numbers" in which overcrowding was the major factor in decision making.
Mr Sean Aylward, responsible for prison operations, said the number of serious offenders - serving three year sentences or longer - had doubled over the last five years. "When we're trying to pick people to let out, the job is getting harder," he said. "On a bad day we could let as many as 50 people go."
He said the typical figure was between 20 and 30 early releases daily, some of which might be "planned" releases rather than a response to new prisoners arriving from the courts.
Most releases come from the 24 per cent of the prison population serving terms for traffic and other offences deemed minor, and the 12 per cent convicted for failure to pay fines or civil debts.
The officials were introducing a programme of prison "open days" for the media, which started yesterday with Mountjoy in Dublin.
Mr Aylward said overcrowding had impeded efforts to introduce rehabilitation and other schemes in prisons, but the Department was placing its hopes in a building programme which would bring the prison population up from 2,300 to about 3,000 over the next three years, at a total capital cost of more than £135 million.
The officials said the overtime bill for prison officers for 1996 amounted to £18 million, or about £7,500 for each officer. However, new legislation would reduce incidence of escorting prisoners to and from courts, which should lower the overtime bill. There are plans for a court building at the gates of the new Wheatfield remand prison in Dublin, accessible by tunnel from the prison, to reduce the transporting of prisoners.
Officials also revealed a British consultant has been hired by an expert group planning the structure of the new prisons board, an independent agency to run the system announced by the Government last year.
The group includes representatives of the Prison Officers' Association and is examining "all current costs of prisons, including overtime", according to the head of the Department's prison section, Mr Mick Mellet. It is expected to report by the end of March.
About 9,000 people a year are sent to the State's 14 prisons. There had been fears that up to 800 more would be added annually by the bail law change, but officials said their "guesstimate" was about 200.