Sadiq Khan has called on social media companies to change algorithms that promote violent and misogynistic material, as London launches a £5m programme to tackle the effect of online harms on young people.

The mayor of London also believes the state should be ready to intervene where platforms cannot or will not change their recommendation systems, and wants Ofcom to enforce the Online Safety Act more aggressively, a person familiar with his thinking said.

The announcement comes before ministers are expected to set out further details of the UK’s under-16 social media ban on Wednesday. The package is expected to include overnight curfews and autoplay being switched off by default for users aged 16 and 17.

However, the government is not expected to provide further clarity on its definition of social media or which smaller services will be exempt.Tech companies have warned that broad rules could pull educational, gaming and other user-to-user platforms into the ban.

“Enough is enough,” said Khan. “Online platforms must set out publicly how they will adjust algorithms or face the consequences.”

The mayor’s Violence Reduction Unit will invest £4.9m in digital youth work, mentoring for girls and young women, training for parents and teachers, and programmes that help young people challenge harmful behaviour online.

The funding will also support local programmes in six London boroughs, which have not yet been selected.

Research commissioned by the unit claims that social media increased the scale and visibility of disputes between young people, creating pressure to respond and making conflicts harder to leave.

It also identified an association between rises in misogynistic posts and police-recorded violence against women and girls on the same day. The researchers said the results did not prove that the online material directly caused the offences.

The analysis tracked public posts on X because it was the only platform that provided usable location data. City Hall now wants TikTok, Instagram and Snapchat to provide researchers with comparable information about how content spreads locally, a person familiar with the matter said.

Lib Peck, director of the Violence Reduction Unit, said algorithms were “funnelling young people towards violent content”, and escalating disputes that began online.

Age checks and curfews pending

The government’s expected announcement follows a study of more than 300 families that tested overnight social media curfews, full removal of apps, algorithmic changes and daily limits.

The Department for Science, Innovation and Technology said teenagers who stopped using social media reported better sleep, improved concentration and lower stress. The study was government-backed and involved families volunteering to impose restrictions at home, rather than the enforcement of a national ban.

“When children spend less time on social media, the benefits are real,” said tech secretary Liz Kendall. “They sleep better, focus more and spend more time with friends and family.”

The department also said between seven and 10 per cent of children had used virtual private networks to bypass age checks, while entering a false date of birth remained far more common.

“Not every young person has a passport or national identity document”, Andy Lulham, chief operating officer at age-assurance firm Verifymy, told City AM. “Modern methods such as email-based checks and facial age estimation need to be included so users have alternatives where one route is unavailable or inconclusive.”

Civil liberties groups have warned that widespread age checks could result in more identity documents and biometric information being collected online.

Age-assurance providers argue platforms can confirm that a user is above a threshold without establishing their identity.

John Lucey, vice-president for northern Europe at digital forensics company Cellebrite, told City AM: “Teenagers will find a way to use technology with or without permission. Restricting access can move activity underground, and it can be as simple as lying about their age or using a VPN.”

He said that could make investigations more difficult where abuse or other offences occurred through encrypted or poorly monitored services.

“Engagement-driven algorithms can spread harmful material faster than police can investigate it,” added. “There must be preventive measures in place, alongside the ability to recover evidence and build cases when crimes occur.”

City Hall said the new programmes would be measured under the Violence Reduction Unit’s existing outcomes framework. The framework is expected to track the reach and performance of each intervention, building on programmes that have worked with more than half a million young Londoners over seven years.