A notorious prison riot prompted the Government to consider using the military detention block at the Curragh as a general prison.
The revelation came as papers released as part of the State Archive showed the Government was deeply concerned about the implications of a riot by inmates at Fort Mitchel Prison on Spike Island in Cork.
The riot, which erupted on September 1, 1985, saw inmates gain control of large parts of the recently-refurbished island prison.
Prison officers, civilians and gardai were trapped in parts of the Fort Mitchel complex until order could be restored.
At the height of the riot, a fire was started and major damage was caused to the Block A accommodation unit.
A confidential memo on September 5 revealed that the Cabinet had approved a plan for Justice Minister Michael Noonan to use the military detention complex at the Curragh as a general prison if so required.
"The destruction of a major part of Fort Mitchel has meant the loss of about 80 places in the prison system," the memo stated.
The Cabinet was very concerned by the spiralling numbers in Irish prisons and the impact that the loss of 80 places would have.
In 1982, the daily average for people in custody was 1,236. But that had soared to 1,590 for 1984. By September 1985 the number has soared again to 1943.
Mr Noonan informed the Cabinet that the Curragh would be for short-term use only.
However, a separate cost analysis raised serious concerns about using the Curragh as a prison for as few as 30 inmates.
"When civilian prisoners were last in the Curragh they were under military control…and this tied up a large number of army personnel."