Users accessing online pornography in the UK may soon be asked to have their faces scanned, according to measures announced by Ofcom to prevent children from seeing such material.

Enforcement guidance published on Thursday will apply to social media platforms and websites such as OnlyFans and Pornhub, stating that children will no longer be able to simply say they are 18 or older to view pornographic content online.

The communications regulator also said adults must start proving their age through methods such as facial age estimation, credit card checks or matching with photo ID.

Requirements around "efficient" age checks will come into effect this spring for thousands of services that display or publish their own pornographic content. The rules will come into effect in July for so-called peer-to-peer and social media services, with non-compliance potentially attracting sanctions, including fines of up to 10% of a company's turnover.

Research by the Children's Commissioner shows that the average age of British children's first exposure to pornography is 13 years old, with one in 10 viewing pornography by the age of nine. It’s commonplace.”

Ofcom has not yet set the level at which age verification software needs to be effective (eg 90%), but it says this could be done in the future as it continues to take action to enforce the Online Safety Act.

“For too long, many online services that allow pornography and other harmful material have ignored the fact that children are accessing their services,” Ofcom chief executive Melanie Dawes said. "They either don't ask, or if they do ask, the checks are infrequent and easily avoidable. This means the company effectively treats all users as adults, leaving children at risk of being exposed to pornography and other types of harmful content. Today, that's starting to change."

Elon Musk's X site has allowed "the consensual production and distribution of adult nudity or sexual acts" since last June. Meta's Instagram platform, overseen by Mark Zuckerberg, prohibits nudity.

Alumudena Lara, Ofcom's policy director for child protection, said: "No matter where you are based or who your political allies are: if you operate in the UK you need to play by their rules .

"I believe that in a few years we'll look back and wonder: Why did we think kids had access to this content?"

A possible method of age checking could avoid using email addresses for facial scans, Ofcom has said. The system can cross-reference other services associated with the address, such as utility bills and financial institutions, to estimate the user's age.

Instead of cross-referencing the user's face with images stored in a database, automatic facial age estimation estimates age based on visual features and does not store images. Such software is already used by OnlyFans, a British subscription platform known for its pornographic content.

On social media sites, "age restrictions" may apply at the post level rather than the social media account registration level.

However, with thousands of porn providers around the world, cracking down on those who flout the Online Safety Act can be difficult.

"The challenge is if a lot of sites are implementing (this) but then they find out that other sites are not implementing it and nothing is happening, then they say, 'Hey, why am I doing this?'" Lina Ghazal said, Director of regulatory and public affairs at VerifyMy, which provides checks using email and facial age estimates. "They have a real challenge to ensure Ofcom implements it fully and effectively."

The new rules also mean websites must not allow any pornographic content to be visible until age checks have been completed. Ofcom said platforms must ensure privacy rights are respected and adults can still access legal pornography, but it said it would "not hesitate to take action and investigate services that do not participate or ultimately fail to comply".