The Liberal Democrats are to oppose plans to impose strict age regulations on porn sites in the UK's forthcoming Digital Economy Bill – describing the measures as something the "Russian or Chinese governments" would impose.
The proposed law is due for a report-stage vote and third reading in the Commons on Monday afternoon.
It follows the passing of the controversial Investigatory Powers Act earlier this month, which the Lib Dems have said "already has the potential to undermine online privacy".
Brian Paddick, Liberal Democrat Shadow Home Secretary, said: "Liberal Democrats will do everything possible to ensure that our privacy is not further eroded by this Tory government.
"Clamping down on perfectly legal material is something we would expect from the Russian or Chinese governments, not our own. Of course the internet cannot be an ungoverned space, but banning legal material for consenting adults is not the right approach."
The Internet Service Provider Association has also said moves to force providers to block adult sites that do not age verify has the potential to "significantly harm the digital economy".
ISPA chair James Blessing said: "The Digital Economy Bill is all about ensuing the UK continues to be a digital world leader, including in relation to internet safety. This is why ISPA supported the government's original age verification policy for addressing the problem of underage access of adult sites at source.
"Instead of rushing through this significant policy change, we are calling on government to pause and have a substantive discussion on how any legal and regulatory change will impact the UK's dynamic digital economy and the expectations and rights of UK Internet users."
Speaking at the ISPA conference last week, Matthew Hare, chief exec of small broadband provider Gigaclear, said he was worried that government legislation was turning ISPs "from carriers of content, to policers of content".
Other aspects of the Digital Economy Bill have also been subject to criticism – most notably proposals to increase the government's sharing of personal data.
Last week academics and privacy campaigners signed an open letter calling for those measures to be removed. ®