Age checks should be carried out by pornography websites before granting access to users, an industry regulator said.
Laws need to be changed in order to protect children from seeing adult material on the internet, online video regulator Atvod, the Authority for Television on Demand, said.
Research for Atvod found that 6% of children aged 15 or under had accessed an adult website over the course of a month.
One pornography website was visited by 112,000 boys in the UK aged between 12 and 17, while some 5% of visitors to adult sites were under 18.
The statistics emerged after the online habits of 45,000 desktop computers and laptops were monitored over a month, with volunteers reflecting a cross-section of the population.
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