The UK Big Tech warning gives Apple, Google and other technology companies three months to stop children from sending or receiving nude images on phones and tablets.
The Home Office said Monday that companies must introduce safety features to block children from taking and accessing naked photos. It said the government would legislate if firms do not act.
Prime Minister Keir Starmer told London Tech Week that the companies had the technical ability to solve the issue. He said the government would change the law if it chose not to act.
The Labour government said technology firms had a moral responsibility to protect children from coercion, abuse and sextortion.
The Home Office said future legislation could include fines for non-compliant companies. It said tech bosses could also face possible criminal liability.
The government cited Internet Watch Foundation analysis showing 91 per cent of online child sexual abuse reports in 2024 contained self-generated content from children.
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The Home Office said Apple had introduced UK age-verification requirements and default safety features for users under 18.
However, it said nudity detection did not cover cameras, third-party messaging apps such as Snapchat or search functions.
The UK media has reported that Starmer may soon announce a ban on children under 16 accessing some social media platforms. Australia became the first country to ban under-16s from social media in December.