Ministers have taken a further step towards enforcing age verification for the use of online pornography in the UK from next spring.
Under new powers contained in the Digital Economy Act, which passed through Parliament earlier this year, a regulator will be able to block porn websites that fail to show that they are denying access to under-18s, for instance by demanding credit card details.
Digital economy minister Matt Hancock has now signed an order allowing the designation of the regulator, expected to be the British Board of Film Classification, to put the new protections into effect from April next year.
The move was welcomed by the National Society for the Prevention of Cruelty to Children (NSPCC), which said watching online porn could be "deeply damaging" to young people. But the charity said that the new measures did not go far enough and there was a need for additional protection for under-18s on social media.
But the Open Rights Group warned that age verification could allow porn companies being able to build up databases of UK users' porn habits, leaving them vulnerable to exposure by hackers.
The new order also allows work to begin on implementing other measures from the Act, including:
:: Requiring catch-up TV and video-on-demand services to provide subtitling and audio description;
:: Cracking down on ticket touts by making it a criminal offence to use bot technology to sweep up tickets for resale at high prices;
:: Improvements to digital connectivity for consumers in hard-to-reach parts of the UK.
Mr Hancock said: "The Digital Economy Act is about building a strong, safe and connected economy. It will secure better support for consumers, better protection for children on the internet, and underpin a radical transformation of Government services."
The Act does not specify the means of proving age for access to adult content online. The regulator will be required to ensure that methods are "robust" and go beyond simply ticking a box or typing in a date of birth to say that the user is over-18. It is thought that initially credit card data will be used, but other methods will be adopted as technology develops, possibly including links to the electoral register.
Adult sites based anywhere in the world will be required to show that they are verifying users' age. Failure to do so could result in a bar on credit card payments from the UK or a block from being carried by UK internet service providers.
An NSPCC spokesman said: "Watching online pornography can have a deeply damaging effect on young people, their behaviour and their understanding of healthy relationships.
"Robust age verification and regulation for online pornography are important first steps in keeping children safe online. But these steps do not go far enough.
"The NSPCC is calling for social networks to be required by law to give under-18s safe accounts with extra protections built in, so that children are kept as safe online as they are in the real world."
Will Gardner, chief executive of internet safety charity Childnet 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."
The executive director of the Open Rights Group Jim Killock warned the new rules could lead to a repeat of the 2015 Ashley Madison scandal, when a database of users of a dating website for people seeking extra-marital affairs was hacked.
"Age verification could lead to porn companies building databases of the UK's porn habits, which could be vulnerable to Ashley Madison style hacks," said Mr Killock.
"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."