A survey has found that parents routinely allow children as young as six to surf the Internet without supervision.
According to the poll of 20,000 broadband users, among six-year-olds, one child in six browses the web alone for up to an hour a day.
For seven-year-olds, the proportion raises to two in five - and across the six- to 17-year-old age group, around half of all Internet activity is carried out without supervision.
Many parents claimed they do not need to monitor their activities, as it mostly consists of social networking or listening to music.
Others said they have security measures in place to limit the kind of websites their children can visit, or routinely examine their Internet browser history to check what they have accessed.
However, research suggests this may not be enough to protect their children from explicit material.
The survey found 14 per cent of six- to 10-year-olds has encountered adult content on the web, either deliberately or accidentally.
Internet service provider TalkTalk conducted the poll. Tristia Clarke, commercial director, said it was "astonishing" that 54 per cent of parents said they "don't have the time or the inclination" to monitor their children's online activities.
"Parents in more affluent homes are a little more likely to let their children surf the web unaccompanied than those in lower income homes," the Daily Mail quoted her as saying.