Tim Farron, the Liberal Democrat President, says David Cameron’s policy of mandatory ‘porn filters’ for internet service providers should be scrapped because “essential sites on sexual health, gender and sexuality, domestic violence and LGBT rights are being blocked”.

Speaking to The Independent, the senior Lib Dem MP said there was growing evidence that the filters were ineffectual and doing more harm than good.

In December, PinkNews revealed that TalkTalk had prevented access to the website of LGBT+ Liberal Democrats through its HomeSafe filter.

Among the content blocked was a feature about Deputy Prime Minister Nick Clegg’s most recent article for PinkNews.

TalkTalk subsequently apologised for blocking access to the site, after the internet service provider (ISP) incorrectly classified it as “pornographic”. 

The day before, TalkTalk had to apologise for blocking access to the website of London Friend, one of the capital’s oldest LGBT charities.

PinkNews also revealed parental controls for users of BT broadband included an option to block “gay and lesbian lifestyle” sites, as well as sexual health information. 

Several ISPs, including TalkTalk, Sky and Virgin, introduced web filters last year ahead of David Cameron’s endorsement of the proposal.

But according to a recent BBC Newsnight investigation, as well as blocking access to several non-pornographic websites, on multiple occasions the filters have allowed access to pornographic websites – thus failing in their primary aim.

Tim Farron, the Liberal Democrat President, has now drafted a motion for the party’s spring conference, calling on the government to drop the policy.

“Essential sites on sexual health, gender and sexuality, domestic violence and LGBT rights are being blocked by these filters, whilst pornographic content is still available,” he said. “Our motion is designed to strengthen Lib Dem ministers’ hands in challenging this nonsensical policy, which has yet to be brought before the House of Commons.”

Mr Farron described the plans as “misconceived, ineffective and illiberal” and said they were designed to win Mr Cameron headlines, instead of protecting children.

“If the prime minister really wanted to protect children from inappropriate material, he’d ensure they had access to good sexual health and relationship education and give parents the help and support they need to talk to their children about this issue,” he said.

The Independent claims sources close to Liberal Democrat leader Nick Clegg have said the deputy prime minister will not attempt to prevent the motion from being adopted when it is debated in March.

But the Tories believe that the party’s tough line on internet pornography will play well electorally and appeal to parents worried about the proliferation of easy to access hardcore images and videos.

Tory sources described the new Lib Dem approach as “disappointing”.

“Tim Farron clearly does not want to prioritise the safety of our children online or support our efforts to prevent anyone accidentally accessing illegal material,” a Tory source said.