Nearly half of all children who have access to the internet have a profile on a social networking site, according to Ofcom, but they are not being protected adequately by parents and internet companies.

In some cases younger children were bypassing the minimum age restrictions on social networking sites. The minimum age for posting a profile on sites such as Bebo and Facebook is 13, but 27 per cent of children aged 8 to 11 said they had social networking profiles, the communications regulator said.