"We would urge the millions of Facebook users around the world to keep looking and to do what they can to help bring these children home.

"This initiative by Missing People, British Telecom and all those supporting them, is another highly commendable and positive step in protecting and helping children."

Missing People has set up an application for Facebook users to download, which will mean information on current appeals will be displayed on their homepage.

The charity is also joining Bebo's "Be Cause", an internet site which gives information for young people about charities and campaign groups, to publicise its 24-hour Runaway Helpline.

It hopes to access millions of internet users in its quest to find thousands of youngsters who go missing each year.