Over 150 people under 18 in Wales were accused of sexual offences against other children in the last two years.
That's according to a Freedom of Information investigation by children's charity the NSPCC.
Three out of the four police forces responded to the FOI request recording 158 cases.
The full number of under 18s offending across the UK was 8,000.
Most victims knew their alleged perpetrator and some of the most common crimes were teenage boys offending against female acquaintances.
Whilst most offenders were male there was a small proportion of female offenders as well as male and female victims.
Crimes included serious sexual assaults, rape, and obscene publication offences.
Up to two thirds of contact sexual abuse on children is committed by other young people.
The NSPCC argues behaviour can be turned around if caught early.
Its harmful sexual behaviour service in Cardiff, Turn the Page, is showing success in helping young offenders change their behaviour and stopping them committing more sexual crimes as they get older.
The NSPCC says it's obtained figures which show that over 8,000 under 18s in England and Wales were accused of sexual offences against other children in the last two years.
One report made to a police force in Wales about a child who was 10 years old.
Welsh Police Forces responded to a Freedom of Information request recording 158 cases of under 18s accused of sexual offences against other children over the two year period.
Most victims knew their alleged perpetrator and some of the most common crimes were teenage boys.
Any adult worried about a child or in need of help and advice can contact the NSPCC's helpline on 0808 800 5000.
Children and young people can contact ChildLine on 0800 1111.
Shaking or being deliberately rough with a baby can cause:
- Learning disabilities
- Brain damage
The NSPCC has launched a new campaign to help new mothers and fathers develop coping strategies when dealing with the pressures of parenthood.
Below is a section of the film from the NSPCC that will be seen by new parents.
A programme aimed at educating new parents about the risks of shaking babies is due to be trialed in hospitals across Wales.
The Preventing Non-Accidental Head Injury (NAHI) programme by children's charity the NSPCC involves showing new parents a short film by midwives and health professionals before they leave hospital.
It will also aim to provide them with coping mechanisms for when the pressures of parenthood get too much.
Health boards in Wales will be among the first in the UK to pilot the scheme.
The NSPCC says that when the DVD was shown in America over a five-year period the number of non-accidental head injuries decreased by 47 per cent.
For more information on the campaign visit the NSPCC website here.