Police launched a Web site on Tuesday to warn children as young as eight about the dangers of putting their personal details on social networking sites such as MySpace and Bebo.
The site — www.thinkuknow.co.uk/cybercafe — has an online cafe where children can learn about the dangers of revealing too much about themselves online.
It warns them not to give away their real name, full address and mobile phone number and to think twice before posting their pictures.
The Child Exploitation and Online Protection Centre, a police agency set up to tackle child sex abuse, said it receives about 10 reports each month relating to children aged between eight and 11.
"We want children to use the Internet," said CEOP Chief Executive Jim Gamble, "but we want them to do it in a way that safeguards their time in the virtual world."
The new site advises children to avoid using a webcam when they talk to strangers online and not to arrange to meet people who contact them in cyberspace.
Children should block strangers who try to add them to their instant messaging contact list, CEOP said.
The site also gives tips on how to safely use mobile phones, chatrooms and email.