One in seven children admit they have bullied someone online, with many doing so to try and fit in, according to a poll.
Others revealed they turned to bullying to avoid becoming a target themselves, or through peer pressure.
Action for Children, which commissioned the survey, said it was “shocking” that online bullying is so widespread, but added it is important to remember that many children bully others because of problems in their own lives.
The poll, published to mark Safer Internet Day, found that 15 per cent of the 2,000 eight to 17-year-olds questioned said they have bullied someone online.
Of these, nearly three fifths (59 per cent) said they did so to fit in with a particular social group, while around 43 per cent said they had done so to prevent themselves from being bullied.
Over a quarter (28 per cent) admitted they had become a bully due to peer pressure and 12 per cent said they had done it because they were unhappy.
The survey also found that nearly half (48 per cent) of the youngsters questioned admitted they had kept silent after seeing or reading something online that made them feel uncomfortable, rather than telling someone.
Around one in five (20 per cent) said they had kept quiet because they were scared of what a bully might do to them, while nearly half (46 per cent) said they were not worried enough to let someone know what they had seen and 17 per cent said they were worried they would get into trouble if they told.
Deanna Neilson, head of child protection at Action for Children, said: “It’s shocking that online bullying is so prevalent, but we must not lose sight of the fact that many of these children bully others because of something going wrong in their own lives, or being driven to it through fear of being bullied or socially shunned themselves. Low self-esteem, stress at school or being victimised themselves by peers or adults are all reasons a child might act out on others.
“It’s important for parents to ask children about the day they’ve had online, just as they ask about the day they’ve had at school – whether your child is being bullied or bullying others, the problem, and any potentially more severe issues surrounding it, must be addressed.”
Separate research by education charity Tablets for Schools reveals that half of secondary school pupils and over a quarter of those children still at primary school have communicated with people they do not know using social media.
It also found that using tablet computers at school increases the likelihood of a young person telling someone after seeing something online that concerned, upset or frightened them.
The wide-ranging survey, which questioned more than 7,000 youngsters, also found that around 70 per cent of secondary-age pupils and half of primary-age pupils take an internet-based device to bed with them.
Secondary school pupils who use tablets at school and at home are less likely to take an internet device to bed with them.
The findings also show that secondary-age children who use a tablet at school, at home, or both, are more concerned about keeping their details private online.
This suggests that they have a greater awareness of internet safety, the charity said.
Overall, half (51 per cent) of the secondary pupils surveyed, and 60 per cent of those at primary school agreed that using a tablet or other device at school every day has made them more aware of using the web safely.