One in seven children say they have bullied somebody online, with many admitting they do so to avoid being targeted themselves.
The poll commissioned by the charity Action for Children reveals how widespread bullying has become online, with stress and low self-esteem cited as reasons some children target others.
The survey found 15% of the 2,000 eight to 17-year-olds polled said they have bullied somebody on the internet.
Some 59% said they bullied others to fit in with a social group, while 43% said they did so to prevent themselves from being targeted.
A quarter of respondents said they became a bully due to peer pressure and 12% said they bullied others because they were unhappy.
The results of the poll have been published to mark Safer Internet Day.
It comes as a separate survey found half of secondary school pupils and more than a quarter of those at primary school have communicated with a stranger on social media.
The research by the charity Tablets for Schools found using tablet computers at school increased the likelihood of a young person telling someone after seeing something upsetting online.
The survey of 7,000 youngsters also found around 70% of secondary-age pupils and half of primary-age pupils take an internet-based device to bed with them.
Â