Sir Keir Starmer has issued an ultimatum to Apple and Google: activate built-in features to block children from taking, sending or viewing sexually explicit images on smartphones and tablets, or face legislation that could impose fines and even criminal liability.
Speaking at London Tech Week, the prime minister said: "This is not an impossible challenge. These are some of the most innovative companies in the world and I believe they can solve it."
“Starmer tells Apple and Google to block nude images on children's phones or face fines and criminal liability.”
The government has given the tech giants three months to comply voluntarily. If they do not, it said it will bring forward legislation to force the activation of such features. The prime minister said the changes would apply to both existing and newly-sold smartphones and tablets in the UK.
"Legislation could cover operating system providers and others in the supply chain, such as retailers, and will not affect the use of devices owned and used by adults who verify their age," he said.
A Google spokesperson responded: "We are deeply committed to protecting children online. We are working constructively with UK partners to find effective, privacy-preserving solutions that deter the spread of harmful content while ensuring a safe digital environment for young people."
Apple has not responded to the BBC's request for comment.
A number of tech companies already have methods in place. Apple recently began asking UK iPhone users to verify their age to ensure only adults access over-18 content. It also offers a "Communication Safety" feature that warns children with a Child Account when they send or receive nude images across Messages, AirDrop and FaceTime. The tool is turned on by default for those under 18 with a Child Account, and parents can enable it for teens in iCloud Family settings. It lets children report nude images to Apple and directs them to help and support.
Google's own Messages app, running across Android handsets, has similar settings to blur sensitive content for users supervised by a parent or guardian.
The government has highlighted an AI tool developed by safety tech firm SafeToNet as showing how firms can safely scale on-device detection and blocking of nude images for children.