Facebook is the worst social networking site for Internet trolling, a study has said.
The study, for Internet site knowthenet, found a number of social networking sites had become "popular forums" for trolls, and bullying is now more prevalent online than anywhere else.
The report showed that some 87 percent of teenagers who reported cyber abuse said they were targeted Facebook, while around one fifth of youngsters were picked on by Twitter trolls, Sky News reports.
According to the report, 49 percent of those targeted by bullies were victimised off-line, while 65 percent of teenagers were subjected to abuse in cyberspace.
Only 37 percent of those who had experienced trolling ever reported it to the social network where it took place, the report found.