It is quite simply staggering that up to one in three sexual assaults on children are committed by other children.

Last year police forces in England and Wales who replied to our FoI request had dealt with at least 5,000 cases of child sexual abuse committed by other children (under 18s). I say at least 5,000 as the slightly chaotic manner in which this crime is often recorded means that many forces couldn't even give us a figure.

And of the ones that did reply, some only recorded cases that had been solved (or 'disposals' as they put it) as opposed to all reported crimes. So even getting a measure of the situation has taken a huge amount of work before we even begin to look at tackling it.

And sex offenders are often seen as adult men targeting, grooming and abusing children but the fact is that children and teenagers are far more likely to know their attacker than not and, increasingly, the attacker is likely to be a peer such as someone they know from school. Where the relationship between victim and abuser was recorded (again, they often didn't have this information), in 80% of cases the children were known to each other.

This echoes what young people are telling us through ChildLine and focus groups about the dangers they often fear being from other young people or older children and teenagers.

But what we do know is that the numbers are alarming. And sexual violence in teenage relationships remains hugely underreported but something that is a very real concern for many girls, and also some boys.

We're concerned at the NSPCC that easy access to hardcore pornography is warping young people's views of what is 'normal' or acceptable sexual behaviour. Adults have a choice about what to watch within the law, but my concern is that the internet is exposing ever younger eyes to things they are just not yet ready to process. They are learning about sex from porn and not from proper respectful relationships. Much of the material is violent and simply vile; it paints a picture of sex as one sided that has no basis in love or respect. Just last week two boys were jailed for raping a girl after watching violent pornography on the internet.

And a recent focus group set up by the NSPCC and Plymouth University found that many young people actually saw online porn as so common it was mundane. Fourteen and 15 year-olds almost bored of porn they see so much of it!

But this isn't just about technology. Many of those who offend will be highly damaged individuals who have suffered contact sexual abuse themselves. They then act out this abuse on younger children.

What these young people do is horrific and we support proper punishments to deal with their crime. But most can be identified early, will not necessarily grow into adult abusers, and are not a lost cause. There are nearly always opportunities to stop this behaviour as soon as it's noticed, before it escalates into physical attacks, and before they become adult offenders.

At the NSPCC, as well as supporting those who have suffered abuse to rebuild their lives, we also work with child offenders to change their behaviour. Our 'Harmful Sexual Behaviour' service aims to stop those young people displaying inappropriate or precocious sexual behaviour from offending or growing into adult sex offenders. It's not easy to work with perpetrators but unless we turn this behaviour around there will be more victims. Programmes are already operating in several locations. If successful, we hope to roll this out across the country.

But these services are expensive and it's not just those at the hard end that we need to get through to. The most recent data suggests up to a third of teenage girls and one in six boys have suffered some form of partner sexual violence. This shows a need to educate all our young people about what is appropriate and what isn't. Parents, teachers, youth workers and anyone who works or volunteers with children and young people must keep an eye out for aggressive sexual behaviour and challenge it straight away.

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