Several judges and the Garda Commissioner have called for changes to the probation and welfare service, particularly for young offenders.
In submissions to a government-appointed expert group, judges said young offenders who are unsuitable for prison are receiving jail sentences, while other prisoners who should serve longer sentences are being released early.
The judges told the Expert Group on the Probation and Welfare Service the needs of young offenders were not being met, and increased reoffending was the result.
A Dublin Circuit Court judge, Mr Pat McCartan, said if there was "an expanded and fully resourced probationary service" judges would have an "alternative to incarceration". He said it was "frustrating" for judges not to have access to effective non-custodial penalties.
The expert group recently issued a report calling for major changes and the Minister for Justice, Mr O'Donoghue, is examining the report. He has already stated that 39 new probation and welfare officers will be hired. Submissions to the group were obtained by The Irish Times under the Freedom of Information Act.
Judge McCartan told the group: "It is a fact that there are many prisoners in jail at any one moment that might be better dealt with outside prison.
"Conversely there are many prisoners being released too early primarily because of the shortage of prison spaces".
In his submission to the group, the Garda Commissioner, Mr Pat Byrne, said he could see the "necessity" of input into probation and welfare service from some body independent of the Department of Justice, Equality and Law Reform.
He said criminal behaviour should be tackled by a "complex range of solutions". He said the work of probation and welfare officers, who look "behind the criminal behaviour" was necessary, practical and vital.
The service also needed administrative back up in order to minimise the time spent on non-core activities, he said. More formal structures were needed to link the Garda's programme dealing with juvenile offenders - the Juvenile Liaison Officers (JLO) scheme - and the work done by the probation and welfare officers.
He said JLOs had "vast amounts of information" on juvenile offenders which could be of benefit to the probation and welfare service, but needed formal structures to be set so it could be exchanged.
On early release, Judge David Riordan of the Cork District Court said "it would appear that prisoners who are given custodial sentences are released from custody without any further reference to being under the control of anybody in authority".