Parents are letting their children wander around cyberspace with no protection or supervision, according to a study published this week.

Despite government warnings that children going online can be vulnerable to bullying, paedophiles or images of sex and violence, two-thirds of families have no parental controls on home computers, according to the website Mumsnet.

Such controls, either built into computers or on separate software, can block specific sites and material, and limit the time spent on terminals.

In a study of nearly 1,500 parents, Mumsnet found 70% of teenagers were allowed unsupervised access to the internet; 37% of teenagers had a computer in their room; 35% had talked to strangers in chatrooms, and 18% of parents had no idea if their children met strangers online.

Justine Roberts, co-founder of Mumsnet, said: “Our audience is quite net-savvy, by definition.

“I am surprised by how many people had done nothing to control or supervise their children’s use of the internet.”

More than half of parents said they were worried about the online content their children might encounter, with sexual images the main concern. A fifth of parents of 10 to 12-year-olds were aware their child had seen sexual material.

Last week, the Byron Review, a government report on child safety online led by psychologist Dr Tanya Byron, recommended better education for parents.

A report out this week adds a concern from young people themselves – that surfing the internet is harming their interpersonal skills.

Jonathan Kestenbaum, chief executive of the National Endowment for Science, Technology and the Arts, which carried out the research, said: “Employers are anxious the obsession with qualifications and online skills is obscuring social skills.

“We found young people were saying the same thing.”