More than half of children using the internet have had an "unwanted experience" online as the trend of using social networking sites increases, according to a new poll.
The survey for the NSPCC found 50.4% of children had such an experience, which could mean anything from being bullied or threatened to being asked to perform sexual acts.
More than half of children (52%) now use sites such as Bebo and MySpace at least once a day, according to the poll, heightening their exposure to those who could potentially abuse them for their own ends.
The top reason cited by young people for logging on to the sites was to make new friends (89%) and to link up with people they already knew (79%).
But the survey for children's charity also showed almost 60% of children resort to them to stop themselves feeling alone and 53% use them to share their problems.
The findings of the online poll of 2,053 children mostly between the ages of 11 to 16 were revealed as this year's Don't Hide It campaign is launched.
It aims to encourage children to speak out about all forms of abuse perpetrated through social networking sites, following on from last year's campaign about sexual abuse.
NSPCC director and chief executive Dame Mary Marsh said: "Children face real threats on the internet such as sexual grooming, cyber-bullying, exposure to violent, pornographic and other unsuitable material and being lured into dangerous real-world situations.
"Online social networking is part of millions of children's lives. We must recognize and respond to this reality by helping them be safer online as well as helping them speak out about abuse at the same time."
Previous research has shown that one in three young people regularly using the internet have received unwanted sexual comments, according to the NSPCC.