Almost half of all UK children who have access to the web (49 percent) have a profile on a social-networking site such as Bebo, Facebook or Myspace. And around 41 percent of these children are at increased risk because they do not use the provided privacy settings.

According to research from Ofcom, 49 percent of web-enabled children aged eight to 17 have a social-networking profile. By comparison, only 22 percent of adults are actively involved in online social-networking.

Around 41 percent of children with profiles leave their privacy settings open - because of this, their images and private data are visible to anyone with a web connection. Even more disturbingly, around a third (34 percent) of 16-24 year olds are happy to give out their phone numbers and email addresses.

"There are huge benefits to internet use, and we do not want to be too scared about the dangers. But parents who allow children to go online without supervision need to recognise that they are potentially at risk." said Ofcom's Robin Blake.

"When children go out to play, parents often state ground rules about when they come back. Parents need to recognise that going online has the same kind of risks."

Bebo is the most used social-networking site with children aged between eight and 17, Facebook is most popular with adults followed by MySpace.

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