A help button for helping children being bullied online must be introduced, popular social networking websites Facebook and MySpace have been told.
The outrage comes after rival networking site Bebo adopted the button that allows users to contact trained child protection officers and also provides details of local police and links to 10 other sources of help.
Jim Gamble, from the Child Exploitation and Online Protection Centre (Ceop), criticised MySpace and Facebook for not following the same example of Bebo.
He said there was "no legitimate reason" for not doing so and that social networking sites were raking in money through advertising by attracting children and teenagers to join.
"We applaud that but do not forget while you do that there is a responsibility, a duty of care, to the young and the vulnerable," The BBC quoted him as saying.
He added: "[The button] is tiny and does not take up any significant real estate. The bottom line is there is no legitimate reason for not taking it and placing it on a site."
Sir Hugh Orde, president of the Association of Chief Police Officers, also said: "I can see no reason why other sites would not consider adopting the same approach and would encourage them to embed the Ceop Report button for the benefit of all users."
A Facebook spokesman, on the other hand, explained: "The safety of Facebook users is the top priority for the company, which is why we have invested in the most robust reporting system to support our 300 million users.
"We also work closely with police forces in the UK and around the world to create a safe environment. Our teams are manned by trained staff in two continents giving 24-hour support in 70 languages.
"We look forward to hearing about the experience of Bebo using the Ceop button and will take account of their experience in any future evaluation of our reporting systems."