A comparison of international prison trends done by the British Home Office shows Ireland has the third-fastest growing prison population in the world.
The report says the prison population here rose by 23 per cent between 1997 and 1999. Only Greece and South Africa had bigger increases. The average rise in Europe is 5 per cent.
There are 3,091 prisoners in custody in the State compared to 2,442 in 1997.
The increase in recent years is attributed to an increase in sex offences, a reduction in the number of prisoners on temporary release and longer sentencing.
An Irish Prison Service spokesperson told ireland.comthat in recent years there has been a "substantial increase" in reporting rates both for recent sex offences and child abuse offences dating from further back.
Five years ago the number of inmates being held for sex offences was 200. It now stands at 395 or almost 1 in 7 of the prison population.
The number of prisoners on temporary release has fallen from 550 in October 1996 to less than 200 this year.