Almost one in five prisoners serving life sentences were doing so outside of jail last year, according to figures released by the Department of Justice.
Under the Irish penal system, the Parole Board is entitled to decide that inmates serving life sentences can be released from prison either temporarily or to complete the remainder of their sentence under the watch of the Probation Service.
Some 80 people were serving life sentences outside of a prison setting in December 2015, while 331 did so in State custody.
The latter figure is down from the end of 2014 when 344 prisoners were in jail serving life sentences, but there has been a general upward trend in the number of life sentences given over the last decade, with 193 such sentences being served in 2004.
Political parties
The Department of Justice figures show six prisoners were released to serve life sentences in the community during 2015.
The issue of parole is a controversial one and, following sustained criticism from political parties and penal reform groups, the Oireachtas earlier this year published the Parole Bill 2016 put forward by Fianna Fáil TD Jim O'Callaghan which, if passed, will put the Parole Board on a statutory footing.
Commentators have previously expressed concerns that the board is composed of too many political appointees, with Fianna Fáil's John Lahart telling a recent Oireachtas debate that the current 60-year-old parole system is "outdated and in urgent need of reform".
Prisoners in the community who violate their terms of release can be taken back into custody on the order of the Irish Prison Service, and An Garda Síochána can also recommend returning an individual to a detention facility if they breach any conditions.
Average time served
Latest estimates put the average length of time served for a life sentence at 17.5 years, up from around 11 years in 2003.
Commitments to restructure the Parole Board have followed on from recommendations made by the Penal Policy Review Group’s report in 2014 which advised that the board should be given statutory status to encourage greater transparency and accountability in its operations.
Minister for Justice Frances Fitzgerald has repeatedly stated that she has no intention of introducing a specific minimum term of imprisonment for murder as has been called for by some victims' rights groups, or replacing the offence of manslaughter with different degrees of murder.