"Incomprehensible" terms and conditions of social networks mean children have little idea what they are signing up to, the Children's Commissioner in the UK has warned.
As she publishes a year-long study into children and the internet, Anne Longfield said youngsters were left to "fend for themselves in the digital world".
She said government should teach children "digital citizenship" from the age of four as part of the curriculum, and that children should have a digital ombudsman to help them remove content from social media companies.
Ms Longfield told Sky News: "The internet is an extraordinary good. But it's developed very fast and it's developed in a very disorganised way.
"It wasn't developed for children, although children are some of its biggest users."
In Ireland, a new report shows that 86% of primary school children in Ireland use a mobile device.
Irish firm Zeeko has put together its second School Digital Trend Report, with almost 4,500 primary school children having completed its questionnaire in late 2016.
The results show that 86% of children have access to a smart phone, tablet or iPod, The report found that 34% of primary school children have more than two hours screen time per day during weekdays, which increases to 54% of children at weekends.
Joe Kenny, Zeeko founder and CEO said: “There is no doubt the internet is a hugely beneficial resource for young people and something they will use more than the current generation. Internet safety is all about education.
"Particularly for younger children it is important to raise their awareness of online risks to give them the protection and coping strategies which will help them become confident digital citizens," he added.
In 2018, a new EU law, the General Data Protection Regulation, will force technology companies to spell out how they use people's data much more clearly.
The UK government has said it will implement the regulation, regardless of Brexit.
