The penal system is helping to marginalise and criminalise people from an early age, according to Fine Gael's spokesman on justice, Gay Mitchell.
Mr Mitchell was speaking after the publication of a report by the Department of Justice on the Irish prison system.
"Criminal acts cannot be excused, but this new report on the prison system reveals that there is a very real problem with repeat offending. Locking prisoners away in poorly equipped prisons is not the answer; it only alienates and excludes them further from society," Mr Mitchell said.
"If we continue as we are we will have an ever-increasing number of offenders and therefore even more victims. This is in nobody's interest," he added. Mr Mitchell said that the argument for prison reform is now "overwhelming".
The report - entitled A Study of the Number, Profile and Progression Routes of Homeless Persons Before the Court and in Custody (2005)- was funded by the Department of Justice and commissioned by the Probation and Welfare Service.
It found that half of the State's prisoners have a history of homelessness, and that significant numbers of inmates are chronic drug-abusers who have been diagnosed as psychiatrically ill.
Its authors recommend that community-based sanctions be more fully developed, saying imprisonment should be used only as a last resort for many offenders.