Twenty people are being sent to prison every day for failing to pay fines.
Figures released by the Department of Justice show 7,500 people were jailed in 2012, at a cost of more than €2m.
The figures have more than trebled since 2008, when just 2,500 individuals were imprisoned for the non-payment of fines.
Liam Herrick of the Irish Penal Reform Trust said the system makes no sense.
"It's difficult to fully quantify the amount of garda time wasted by going to people's houses, arresting them and bringing them to prison, knowing they'll be released a couple of hours later," he said.
"Also for the prison service, the time spent processing people's medical examinations and that's involved in the committals process."