Teenagers are uploading their own sexual images onto the internet, according to an expert on online abuse.

The traditional idea that middle-aged men are the ones putting up the images and grooming children for sexual exploitation is "wide of the mark".

A conference of forensic psychology at University College Cork has heard that a growing number of sexually explicit images of young people are being put on the web by the teenagers themselves.

"Here we call it grooming, but in the United States it is known as sexual solicitation and research there shows that about half of all solicitation is done by juveniles," Dr Ethely Quayle of the Combating Paedophile Information Networks in Europe (COPINE) told the conference.

"Girls who use chatrooms are most at risk and people who are personally troubled or in conflict with their parents are particularly vulnerable," she said.

Dr Quayle said the sexual images came from sources such as old photographs and videos. Many of them were Scandinavian from the 1970s. There were domestic and commercial images and those taken with hidden cameras.

A growing number, however, were found to be generated by teenagers themselves and either put on sites like Facebook, and Bebo or sent via mobile phones.

"As a result we are seeing the increasing criminalisation of children but that is not the answer," said Dr Quayle.

The expert cited the case of Adrian Ringland, a 36-year-old British paedophile who used internet chatrooms to hack into the computers of teenage girls.

Dr Quayle stressed that the internet is a medium which lacks adequate guardianship. Her concerns were re-inforced by Mick Moran, a criminal intelligence officer with Interpol in France. Mr Moran helped to capture Canadian Christopher Neil, the world's most wanted paedophile, last October.

"We need to de-technify the internet," said Mr Moran, who explained that new technology was in danger of surpassing the ability of law enforcers to deal with internet crime.

"The internet is all about speed and fluidity of information, yet many police services do not even possess an email address or have access to the internet," he added.

Mr Moran also said information needed to be shared more quickly. "At the moment it is largely paper-bound and police and governments are sticking their heads in the sand."