There is more staff than prisoners in the State's 16 penal institutions, according to figures issued by the Minister for Justice, Mr O'Donoghue.

The figures, based on calculations made on July 3rd this year, show that there were 3,148 staff and 3,095 prisoners, a ratio of 1.02:1.

The costs were calculated last year.

In Portlaoise Prison there are 2.46 staff for every prisoner. Portlaoise is also the State's most expensive institution because it costs an average of £124,300 to keep each inmate there, compared to the national average of £59,570. Mountjoy Prison has 622 staff and 580 prisoners and costs £59,200 per inmate.

The least expensive institute was Loughan House, Co Dublin, for young offenders, where it was £42,200 for each inmate. It has 49 staff and 78 offenders.

In a written reply to Mr Richard Bruton (FG, Dublin North Central) the Minister pointed out that the costs were based on keeping an inmate 24 hours a day 52 weeks of the year.