Measures to force pornography sites to check the age of UK viewers have been unveiled, signaling the next step in a government crackdown on adult online content.

The ID checks are due to be part of the Digital Economy Act, which encompasses the introduction of age-verification rules for sites that provide porn “on a commercial basis” to UK viewers, as well as the introduction of a regulator to check sites are complying with the new rules.

That regulator is believed to be the British Board of Film Classification (BBFC), which polices age limits on films and video games. It will be the regulator’s responsibility to oblige porn sites to maintain age-restriction barriers, with a likely punishment for incompliance being the threat of blocked access from internet service providers (ISPs). While it’s believed the BBFC will be appointed, the Department for Digital, Culture, Media & Sport said specific details wouldn’t be finalised until the autumn.

Also waiting to be finalised are details of how enforcement would work. According to the Mail on Sunday, sites could also face £250,000 fines for failing to comply. The paper also claims that users will need to prove their age by providing details from a credit card – which cannot be legally issued to anyone under the age of 18. The plan is for the measures to be rolled out across all porn sites by April 2018.

The minister of state for digital, Matt Hancock, began the official process on Monday by signed the commencement order for the Digital Economy Act. Ahead of this, he claimed authorities were “taking the next step” to ensure there is a legal requirement for adult websites to ensure content is “behind an age verification control”.

“All this means that while we can enjoy the freedom of the web, the UK will have the most robust internet child protection measures of any country in the world,” he said.

The measures look to have the backing of advocacy groups for child safety. An NSPCC spokesperson told Alphr: “Watching online pornography can have a deeply damaging effect on children and teenagers development, both in how they think and behave.

“This is why having workable and enforceable measures that will protect them from adult content on the internet are a vital part of creating a safer online world for young people.”

Will Gardner, the chief executive of internet safety charity Childnet, said that steps to restrict child access to adult content “are key”.

“It is essential to help parents and carers, as well as young people, be more aware of this risk and what they can do to prevent exposure and also to make sense of exposure if it happens.”

While the Digital Economy Act became law in April, a number of groups have criticised the legislation for being draconian and breaching the privacy of their users. Amongst the criticisms was the concern that, by providing personal information to access adult content, vast pools of user data could be misused – either monetised for personal gain by the companies themselves, or leveraged as blackmail by hackers.

“Age verification could lead to porn companies building databases of the UK’s porn habits, which could be vulnerable to Ashley Madison style hacks,” Open Rights Group’s executive director Jim Killock told Alphr.

“The Government has repeatedly refused to ensure that there is a legal duty for age verification providers to protect the privacy of web users. There is also nothing to ensure a free and fair market for age verification.”

Killock pointed to porn parent company MindGeek, which runs a raft of services including PornHub and YouPorn. He said there is a risk it will become the “Facebook of age verification”, potentially monopolising the market by creating a shared age-verification login for all its sites. “They would then decide what privacy risks or profiling take place for the vast majority of UK citizens.”