Drugs and alcohol played a part in over half the offences reviewed by the Parole Board between 2011 and 2013.

At the publication of the board's annual report for 2013, Minister for Justice Frances Fitzgerald noted that prisoners are now serving an average of 18 years before being considered for parole.

This compares to a figure of seven-and-a-half years in the 1970s.

The parole board says its caseload was 329 last year, resulting in 95 recommendations.

This is the first time the annual report has been publicly released.