By Nick Triggle
Health reporter, BBC News
Children at risk of sex offending need more help in a bid to reverse the rising number of sex crimes committed by youngsters, experts say.
The voluntary sector runs specialist clinics
Charities say the internet is a growing factor, with children as young as five treated for inappropriate behaviour.
The Youth Justice Board said 1,664 children were given police warnings or court orders for sex offences in 2002-3 - by 2005-6 this had risen to 1,988.
NHS chiefs said services were improving but admitted care was too inconsistent.
The voluntary sector treats most of the children demonstrating what is termed 'sexually harmful behaviour', taking referrals from police, social services and the NHS.
This includes children who have committed sex offences, such as indecent exposure or sex assaults, or, for young children, those who are engaging in acts deemed inappropriate for their age.
The biggest single provider of services is the NSPCC, which runs 22 services in England, Wales and Northern Ireland.
The charity treated over 750 youngsters last year - the overwhelming majority boys - with an average age of 13, although children as young as five were seen by NSPCC specialists in talking therapies.
Numbers have been gradually increasing in recent years, partly due to more awareness over the issue, the charity says.
But officials say they are particularly worried about the role the internet is playing.
Kevin Gibbs, co-chairman of the NSPCC's sexually harmful behaviour group, said: "These children have usually experienced some sort of trauma - sex abuse or violence - which seems to be behind this.
"But what all our services are reporting is that the children they are seeing report having seen abusive sexual images on the internet.
"Five years ago this was just not available to them. It is not so much a trigger, but the problem is that is desensitises them and enables them to tell themselves what they are thinking is okay.
"This is affecting all sectors of society. The children we are seeing come from all kinds of background."
He added better co-ordination was needed between government departments, police and councils to make sure the early warning signs are acted up on.
His comments come after the number of children being warned by the police or ending up with court orders for sex offences increased.
In 2002-3, there were 1,664 cases. But by 2005-6 this had risen to 1,988, according to the Youth Justice Board. One in 10 of the offences were committed by children aged 12 or under.
While most children will be treated by the voluntary sector, the NHS - in partnership with local government - does offer some support through Child and Adolescent Mental Health Services (Camhs), which are situated in a variety of places, including schools, GP surgeries and hospitals.
But Pam Hibbert, principal policy officer at Barnardo's, which runs 11 services across the country, said: "Their waiting lists are very high, and they just don't have the capacity or speciality to deal with these children.
"We need councils to take charge."
Jo Webber, of the NHS Confederation, said: "The service is improving, but there is still too much inconsistency.
"There is some great voluntary sector provision and we need to work in partnership with these bodies to make sure children get the right help."
Tink Palmer, who used to run a service for children who display sexually harmful behaviour and who is now a board member of the Internet Watch Foundation, agreed more co-ordination of services was needed.
But she added: "One of the biggest problems today is with the internet. Some of the most graphic, horrible images are just a few clicks away.
"It is important parents make sure they know what children are doing on computers."