Facebook is facing a backlash from campaigners after announcing it will allow millions of teenagers to open up their profiles to strangers.
The social networking site announced that users aged from 13 to 17 will now be able to switch their settings to share posts with anyone on the internet, rather than just their "friends" or "friends of friends".
Children's groups and internet safety experts denounced the move, saying it could leave young people more vulnerable to cyber-bullying.
Anthony Smythe, managing director of BeatBullying, told The Times: "We have concerns that this age group can now share information in the public domain.
"Something they think might not be harmful now may come back to haunt them later. This is a move in the wrong direction."
The newspaper also said Jim Gamble, former head of the Child Exploitation and Online Protection Centre (CEOP), had expressed "concern" that the move could make youngsters more vulnerable.
It also stressed that initial privacy settings for teens under 18 would automatically be programmed so posts are seen only by friends.
"We take the safety of teens very seriously, so they will see an extra reminder before they can share publicly," the company headed by Mark Zukerburg said in its update.
It already announced last week that it is removing privacy setting so that anyone can search for a user's profile.
A spokesman for the National Crime Agency (NCA), which has recently assumed responsibility for cyber crime, said: "It's important that children and young people manage their online use and understand the consequences of what they share online, especially with anything that is available publicly.
"Robust reporting mechanisms and education messages are vital and we continue to encourage users to report any concerns they have to Facebook, or if their concerns are linked to someone's inappropriate sexual behaviour, to the NCA.
"The NCA welcomes the announcement made by Facebook in relation to the default sharing setting for teens joining Facebook being changed to "Friends", instead of "Friends of friends".
"This will help young people understand the need to manage their privacy settings carefully and to control who they share their information with. "
The spokesman said CEOP, which is now part of the new crime agency, had a "strong working relationship with Facebook and works with them to ensure children and young people are as safe as they can be when using the platform".