Campaigners are crowdfunding a legal challenge against plans to block smut in the UK.

The government last year signed off on controversial plans to require online porn providers to check their users are over 18 before letting them into the site.

The age-verification (AV) measures, ostensibly to stop kids stumbling across sex online, have come under fire from open rights and privacy activists, security experts and pornographers.

They argue that the plan has failed to properly balance the potential benefits with the technical challenges and societal damage it might do.

Today, Backlash UK's campaign, ResistAV, has launched a bid to fund the legal fees to challenge the regime, warning: "It'll be curtains for personal privacy."

Obscenity lawyer Myles Jackman, who is helping lead the campaign, said: "We will send a direct message to Government that violating the citizen's sexual privacy is unforgiveable."

Among the main concerns are that it would allow porn businesses to slurp data on people's sexual preferences – which would make an attractive target for hackers – and risks at the least a very embarrassing data breach.

"Without specific privacy controls embedded in the legislation, there is a very real risk of UK adults' porn habits being outed. The Government's ill-conceived age verification régime puts up to 25 million UK adults at risk," said campaigner Pandora/Blake.

Others are worried that asking people to submit personal details to third parties on the internet risks encouraging poor security practices, or that it will limit people's freedom of expression. Underlying these is scepticism over whether it will even solve the problem.

Campaigners were granted a brief period of respite earlier this year when the planned go-live date was pushed back to allow the regulator, the British Board of Film Classification, to draw up some guidance.

The smut overlord's consultation on the regulatory arrangements and guidance for those who have to comply with the law closed at the end of April but is yet to report back. ®

It is expected that the final versions will be laid before parliament when there is space in the calendar. ®