A Garda programme to help keep young people away from crime without jail-time hasn't worked.
A review has found failings meant that thousands went on to carry out public order, theft and traffic offences.
A small number also committed serious crimes, including cases of rape, sex offences and child neglect.
Gardai say they will apologise to the victims of the young people that should have been prosecuted.
A review of the Youth Diversion Programme found nearly 8,000 incidents of criminal behaviour, involving 3,500 children over the last 7 years were not dealt with properly by Gardaí.
This led to 2,492 people and 988 businesses being affected by crime.
Apology
Letters apologising to victims are being sent out and some will also get a visit from Gardai.
Gardai say the issue arose due to a lack of awareness and training.
It's consulting with the DPP about the cases.
