In the past three years 69 child sex abuse offences were committed by young people under 18, according to Northamptonshire police figures.
The statistics have been obtained by the NSPCC which says that nationally more than 5,000 offences were reported to the police.
It says the true figure will be even higher as not all forces in England and Wales were able to provide relevant data when responding to a Freedom of Information request.
From the 34 police forces that did supply information a total of 5,028 offences were recorded where the perpetrator was under 18, with some as young as five or six. The alleged crimes included rape and other serious sexual assaults which were reported between 2009/10 and 2011/12.
Nearly all, 4,562 of the offenders were boys and, where the relationship was recorded, at least three out of five of the victims knew the abuser. More than one-third of the offences were said to have been committed by a family friend or acquaintance and one in five by family members.
These findings follow a report by probation inspectors last month which found that police, social workers and teachers were missing the warning signs that a child may sexually offend.
The NSPCC, which provides treatment to help reform children as young as five who exhibit signs of harmful sexual behaviour, is warning that easy access to indecent material could be leading to an increase in the number of children needing help.
Claire Lilley, policy advisor at the NSPCC, said: “We hope our findings will ring alarm bells with the authorities that this is a problem which needs urgent attention.
“In some cases older children are attacking younger ones and in other cases it’s sexual violence within a teenage relationship. While more research needs to be done on this problem, we know that technology and easy access to sexual material is warping young people’s views of what is ‘normal’ or acceptable behaviour.
“We are treating an increasing number of children who have carried out online grooming, harassment in chatrooms and ‘sexting’.
“Children who are sexually abusive have often been victims of abuse, harm and trauma themselves. Exposure to this can make them think abusing someone or being sexually violent is ok.
“But evidence shows that most young people who receive behaviour changing treatment early on, such as that offered by the NSPCC, will not continue to sexually abuse others or grow into adult offenders. If we are to tackle this growing problem and protect young victims, more needs to be done to identify and treat children at risk of sexually offending. And we must do more to shield young people from an increasingly sexualised society.”
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.