Britons may soon face identity checks to access adult material on the internet, according to discussions between Whitehall and the private sector.

A scheme proposed by the pornography industry would see adult sites verifying visitors’ identity with organisations such as banks, credit reference agencies or even the NHS.

It comes ahead of an expected new law demanding age checks for online pornography and threatening a block on any sites which don’t comply. It is a key Conservative pledge and has widespread support. But critics say the plans are a privacy nightmare. Some warn they are a step towards Chinese-style internet restrictions.

“This is cutting-edge censorship,” said Myles Jackman, a lawyer specialising in obscenity law. “We are now becoming the world leaders in censorship. And we are being watched very closely from abroad.”

The adult industry is trying to anticipate a new law with a national standard for age checks. The Digital Policy Alliance, which acts for online companies, suggests using information “already on file across central and local government … and/or the private sector”.

This is the state, yet again, intervening in people’s private lives for no reason other than good old British prurience Jerry Barnett, author of Sex & Censorship blog

“Nobody in the UK wants a centralised identity database,” said Dr Rachel O’Connell, an online child safety expert advising the DPA. “The way around that is that Royal Mail knows who you are, your mobile operator knows who you are.”

Adult websites would offer visitors a choice of identity providers – from Vodafone to the Department for Work and Pensions – to vouch for their age, O’Connell said. The user would sign in to the provider with a username and password, and a check would be run against the data it holds.

To boost privacy, checks would pass through an “anonymising hub”. This strips identifying information in both directions of the request. In theory, the provider never knows the reasons for the checks, and the site never knows users’ true identities, just that they are over 18.

British-based sites have had to make stringent age checks since 2010, using credit cards, the electoral roll and credit reference agencies. “It’s a quite intrusive means of identifying age,” said Chris Ratcliff, chief executive of Portland TV, which runs Television X. Many customers simply go elsewhere, he said. He sees the new scheme as an improvement.

But critics warn against any system linking use of pornography websites to identity. Jerry Barnett, a free-speech campaigner and author of the Sex & Censorship blog, said any such system must make detailed records of web-browsing history.

“And we know that privacy in such cases is often breached by accident, by hackers, or secretly by the police and intelligence services,” Barnett said. “This is the state, yet again, intervening in people’s private lives for no reason other than good old British prurience and control-freakery.”

The Conservatives made age verification for online pornography a key part of their election pitch. Checks would “stop children’s exposure to harmful sexualised content online,” the Tory manifesto vowed. “Websites that do not put them in place will be blocked,” Sajid Javid, then culture secretary, added in an election campaign Facebook post.

The law will be an easy win for the new government, even with a slim majority. Few politicians would oppose child protection. Chris Bryant, Labour’s culture spokesman, has already accused the Tories of being slow to act.

Ratcliff, a key member of the DPA’s age verification working group, expects action by the end of the year. O’Connell also sits on the UK Council for Child Internet Safety, which advises the government. She is ensuring that the DPA plan is circulated there.

According to Tory proposals, a regulator would have the power to block sites that don’t use stringent enough checks. Observers believe this will be the Authority for Television on Demand (Atvod), which currently enforces age-check and obscenity rules on UK streaming video sites.

Barnett pointed out that age checks can only work with “draconian” levels of censorship. “I don’t believe Atvod’s plans can be achieved without drastically changing the face of the internet,” he said. Neither the US nor most EU states have gone so far.

Overblocking is also a fear. Facebook has been criticised for censoring pictures of nursing mothers. Filters introduced by British ISPs since 2013, which users have to ask to remove, have blocked sex education sites and even refuges for victims of domestic abuse.

The legal situation is also confused. Ratcliff said it was unclear whether new rules would make content not behind age filters illegal. Jackman added: “As a matter of international law, I don’t understand how it can possibly work. And I don’t understand how it can work under the Obscene Publications Act. It’s just being made up as they go along.”

Britain’s pornography industry has a lot to gain from the government’s plans, critics point out. Tough regulation and stiff competition from abroad have taken their toll on the industry. If overseas sites were blocked it would be boom time for homegrown pornographers.

But foreign web companies are beginning to pay attention, too. Luxembourg-based Mindgeek, which controls the market-leading Pornhub network, joined the DPA’s discussions a fortnight ago. Mindgeek claims as much as 60%-70% of Britain’s audience for streaming pornography, Ratcliff said.

“The important thing now is that it’s going to be a level playing field,” Ratcliff said. “Quite how these foreign websites are going to be brought to task, and how quickly they are going to bring it in, I don’t know.”