More than one in three British teenagers are "extreme internet users" who spend at least six hours a day online, according to a report.
The report, by the London-based Education Policy Institute (EPI) thinktank, said: "Over a third (37.3 per cent) of UK 15-year-olds can be classed as ‘extreme internet users' (over six hours of use a day) -- markedly higher than the average of OECD (Organisation for Economic Co-operation and Development) countries."
"The only OECD country with higher levels of extreme internet use than the UK was Chile."
The report warns that children and young people's heavy internet use can have damaging consequences.
"The evidence points towards a correlation between extreme use of social media and harmful effects on young people's wellbeing. Those classed as ‘extreme internet users' were more likely to report being bullied (17.8 per cent) than moderate internet users (6.7 per cent)," it states.
British children also start going online for the first time at a young age by international standards, the report disclosed.
"Nearly a third (27.6 per cent) of young people in the UK were six years old or younger when they first used the internet," the Guardian quoted the report as saying.
One in three (34 per cent) UK children have experienced cyber-bullying, accessed harmful content such as a website promoting self-harm or had some other type of negative experience when using social media.
"Our research highlights the importance of equipping young people with skills that help them counter emerging online risks. That doesn't mean protecting them from the internet but rather putting forward proactive measures centred on resilience building," the report's author Emily Frith said.