UK internet users are choosing to opt out of the so-called ‘pornography filters’ introduced at the behest of Prime Minister David Cameron.

A new report from Ofcom found that on average only 13 per cent of new internet users chose to activate the software provided by the big four ISPs – BT, Virgin Media, Sky and TalkTalk.

Cameron announced the introduction of the filters in July last year when he warned of the impact the internet was having on children. Since then ISPs have been slowly rolling out the filters, offering them first to all new subscribers, with plans to place an “unavoidable choice” in front of all households in the future.

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Of the ISPs covered in the report just one – TalkTalk – had more than 10 per cent of users agree to the filters. Four per cent of Virgin Media subscribers signed up; five per cent of BT customers; eight per cent for Sky and a 36 per cent of TalkTalk users.

Although BT, Sky and TalkTalk all began to offer “family friendly network-level filtering” by the end of December last year, Virgin Media has been slower to join the pack and the report found that it still only offered filters to around a third (35 per cent) of new customers.

Ofcom say that this is because the majority of new Virgin Media installations involve an engineer visiting the customer’s home – who often ignores or bypasses the filter. Tom Mockridge, Virgin Media’s chief executive, said that the company was taking “immediate action” to rectify this.

The filter categories used by all four ISPs are supplied by third-party providers, with BT offering the most comprehensive blocking including site categories such as “social networking” and “fashion and beauty” and “search engines” – categories that may not be deemed dangerous by all parents.

BT, Sky and TalkTalk all offer varying degrees of customization while Virgin – the ISP with the lowest amount of sign-ups - only gives users an on/off choice.