One in five children in the UK who use social media have been a victim of cyberbullying, with 10 per cent suffering daily abuse, a survey by children's charity the NSPCC has found.
The abuse is not limited to playground bullying. Children also reported threats of serious physical violence including rape, as well as stalking, racism and encouragement of self-harm.
The charity has called for a new strategy to tackle the problem "before it gets out of hand".
The research was carried out through talking to 1,024 11 to 16-year-olds from across the UK and is part of a wider report which will be published in November.
The report also found that a "large number" of children using Facebook, Twitter and Youtube were under the minimum age of 13.
Claire Lilley, the NSPCC's safer technology expert, said: "We are particularly worried about the impact of these risks on younger children, and this is what our forthcoming report will focus on.
"We must ensure young people have the confidence to speak out against this abuse, so that they don't feel isolated and without anywhere to turn."
Lilley added that social networking sites have "a bit of a blind spot" when it comes to dealing with children under 13.
The findings come soon after the death of 14-year-old Hannah Smith from Leicestershire who committed suicide after being sent abuse over question and answer social media site ask.fm.
Following the death, David Cameron called for users and advertisers to boycott "vile" sites that do not deal with cyberbullying.
Latvia based ask.fm has since asked a law firm to carry out a "full and independent audit" and said that its team "ensure genuine concerns are acted upon immediately".