Privacy campaigners have criticised the government’s plans to make porn sites enforce user age verification, saying it could result in “Ashley Madison-style hacks.”

Adult websites will have to install age-verification software or risk being banned under new laws that could see them face £250,000 fines.

Users will have to provide details from a credit card, which cannot be issued to anyone under 18, echoing the verification process used on gambling websites.

The government is also set to announce plans to appoint a regulator for the adult websites, according to the Mail on Sunday.

According to research by Middlesex University, about 53% of 11- to 16-year-olds have seen explicit material online, nearly all of whom (94%) had seen it by 14.

Digital Minister Matt Hancock said: “We are taking the next step to put in place the legal requirement for websites with adult content to ensure it is safely 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.’

Will Gardner, chief executive of internet safety charity Childnet International, said: “Protecting children from exposure, including accidental exposure, to adult content is incredibly important, given the effect it can have on young people.

“Steps like this to help restrict access, alongside the provision of free parental controls and education, are key.

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“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.’

However, Open Rights Group criticised the plans, saying that age verification could lead to porn companies “building databases of the UK’s porn habits, which could be vulnerable to Ashley Madison style hacks.”

Executive director Jim Killock said: “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. We are concerned that the porn company MindGeek will become the Facebook of age verification, dominating the UK market. They would then decide what privacy risks or profiling take place for the vast majority of UK citizens.

“Age verification risks failure as it attempts to fix a social problem with technology. In their recent manifestos, all three main political parties called for compulsory sex and relationship education in schools. Sex education would genuinely protect young people, as it would give them information and context.”

Jerry Barnett, author of the book Porn Panic! and a free speech campaigner, argued that the law wasn’t about protecting children from porn

“It will block any site that doesn’t comply with strict UK content rules,” he said. “Any nude image at all risks being categorised as porn, and the entire site being blocked. Current filtering systems class up to 4m websites as sexual. It’s likely this regime will block the vast majority of these. And doubtless, the censorship regime will then be extended to other crimes against decency.

“Although much attention has been paid to the very dangerous snooper’s charter, this law is at least as dangerous, and has had far less attention.”