Sir Keir Starmer will tell social media companies “to step up and take responsibility” for protecting children after summoning them to Downing Street on Thursday.
The prime minister will hold talks with tech executives at No 10, where he will tell them that the “consequences of failing are stark”.
His warning comes after a report showed that children can still access pornography on Elon Musk’s X platform in an apparent breach of the law.
Ministers are consulting over a possible social media ban for under-16s as well as other measures such as curfews and time limits.
Labour backbenchers are pressuring the government to follow Australia and introduce a blanket ban. However, the government on Wednesday night whipped its MPs to vote down a ban for the second time after it was introduced in the House of Lords by the former schools minister Lord Nash.
The government has said it will decide on the way forward by the summer, after a public consultation ends.
Some social media firms have already introduced features to protect children, but the prime minister has said they must go further.
Starmer said before the talks: “Social media shapes how children see themselves, their friendships and the world around them. When that comes with real risks, looking the other way is not an option.
“Parents rightly expect action and fast. That’s why we’ve already taken the powers needed to move quickly once our consultation ends. I will take whatever steps necessary to keep children safe online. Today is about making sure social media companies step up and take responsibility.
“The consequences of failing to act are stark. We owe it to parents, and to the next generation, to put children’s safety first === because they won’t forgive us if we don’t.”
The meeting comes after researchers from the Center for Countering Digital Hate (CCDH) set up two accounts on X in Britain, as if the users were 13-year-olds. They were then pushed pornography by X’s algorithm.
Under the Online Safety Act, tech companies like X must prevent under-18s from accessing pornography. The report said X had returned explicit content in 15 per cent of posts after the accounts searched for “sex” or “porn”. Some of the content contained oral sex and masturbation.
After the searches, nearly a third of the algorithmically recommended content on the teenage users’ feeds was explicit, with some appearing to depict children and animals, CCDH said.
The accounts were also able to join adult sexual communities and received unsolicited explicit messages. A feature that restricted direct messages was easily turned off by the researchers.
CCDH said that most of the content was circulated by “accounts with few followers” rather than porn producers, whose material is excluded from child feeds because it is labelled.
Callum Hood, head of research at CCDH UK, said: “These findings show X will quickly reshape its ‘For You’ feed to recommend explicit content to young users. Worse, with a single change to account settings, adults can directly message them, leaving children exposed to more explicit sexual material and the risk of grooming.
“Nearly a year after enforcement began, X is still failing to comply with the Online Safety Act, allowing children into sexualised spaces and continuing to host harmful content. How much more evidence is needed before X takes its responsibility to protect children seriously?”
CCDH said there was no age verification in place on the accounts, despite this being a legal requirement for platforms like X.
X is being investigated by Ofcom in Britain and the European Commission over possible breaches of the law in relation to sexual deepfakes created by the Grok AI tool.
The company’s offices in Paris have also been raided by French cyber crime units who are investigating possible complicity in the possession of child sexual abuse material. Musk has called the raid a “political attack”.
X is the only mainstream social media site that permits people to post sexually explicit content, but it places some restrictions on the visibility of such content.
Previous estimates claimed that 13 per cent of the platform is adult content. Last year Dame Rachel de Souza, the children’s commissioner for England, found that X “remains the most common source of pornography for children, outstripping even dedicated pornography sites”.
De Souza said: “Time and again tech companies have shown they cannot be trusted to enforce their own rules. They point to their safety features that look reassuring on paper, but fail in practice.
“My own research has found that as of May 2025, X was the most common source of pornography for children. There is a clear and concerning gap between what the Online Safety Act and Ofcom as regulator expect from platforms like X when it comes to removing harmful content, and what children tell me they are stumbling across online.
“Children should not be expected to police the online world themselves, so we need regulation that reflects the reality of children’s experiences. If companies can’t make their platforms safe for children, they shouldn’t be in them.”
Baroness Bertin, who carried out an independent review of pornography regulation for the government, said: “Some of the findings of this report are deeply shocking but depressingly not surprising.
“It makes clear how much more there is to be done to proactively ensure that companies that provide porn like X are complying with the law. Ofcom must act immediately to investigate this report.”
Ofcom said: “Protecting children is a priority for Ofcom. Under the Online Safety Act, tech firms are accountable for ensuring sites, platforms and apps are safer for the children who use them. They must take a safety-first approach in how their services are designed and operated, including by combatting grooming, tackling child sexual abuse material, and using age checks to prevent kids from accessing pornography.
“Those companies that do not comply can expect to face enforcement action. We’ve launched investigations into more than 100 platforms, including X, and issued over a dozen fines for non-compliance.”
X was approached for comment.
