More than a quarter of eight to 11-year-olds in the UK have a profile on a social network, research shows.
More than a fifth of people in the UK aged 16 and over have an online profile, the Ofcom survey showed.
Most sites, such as Bebo, MySpace and Facebook, set a minimum age of
between 13 and 14 to create a profile but none actively enforce the age
Ofcom's survey of 5,000 adults and 3,000 children found 49% of those aged between eight and 17 have a profile.
The Home Office has been working with social networking firms and is
expected to publish a set of guidelines for the sites around best
practice, security and privacy on Friday.
The report is expected to recommend that profiles created by
children are set to private by default, or are only viewable by friends
nominated by the user.
It also suggests that social sites maintain a distinct contact page
listing contact numbers, such as 999, children can use to get help.
The Home Office guidelines are set to encourage social networking sites
to investigate age verification technologies and to give better
signposting to users about privacy settings, and warnings about the
implications of posting personal details.
Forty-one per cent of children had set their profile so that it was visible to anyone, according to the report.
But 16% of parents admitted they did not know if their child's profile could be seen or not by strangers.