The group of health experts, which includes paediatricians, consultants, family doctors, psychologists and public health experts, explains that excessive use of social media harms children in “multiple ways”, including problems with sleep, vision, speech and language development, and body image.

The letter, which was sent to chief medical officers in Wales, Scotland and Northern Ireland as well as Sir Chris, said: “As clinicians we witness these harmful effects daily, and academics are now establishing causal links.”

The experts cite research suggesting that over one in four children use their smartphone “in a manner consistent with behavioral addiction”, and also mention the dangers of vulnerable youth being exposed to inappropriate sexual content online.

Young people “struggle” with phones

Earlier this year, researchers found that 18.7 percent of teenagers between the ages of 16 and 18 suffer from symptoms of smartphone addiction.

Experts at King’s College London said the fear that mobile devices were harmful was not just “older people hysterical” and warned that young people are “really struggling” because of their phones.

The current advice from the CMO, published in 2019, says that research is “insufficiently conclusive” to develop guidelines for optimal amounts of screen use or online activities such as social media use.

It says it is “not clear” that screen-based activities are the cause of mental health problems in young people, adding that while it is “wise” to take a cautious approach, this must be balanced against the “potential benefits” children may derive from screen-based activities.

The CMO’s advice also says the tech industry should “contribute to the funding” of independent research over the next decade.

Conflict of interest warning

The letter, coordinated by the group Health Professionals for Safer Screens, claims the CMO position is “too lenient” on tech companies and creates a conflict of interest by asking tech companies to contribute financially to harm research.

The minimum age for children to access social media should be raised from 13 to 16, the health experts add.

A government spokesman declined to commit to updating the CMO guidelines, but said: “This government is committed to finding the best way to ensure children are kept safe while benefiting from the latest digital technology.

“We will ensure that there is access to a mental health specialist in every school in England and a Young Futures hub in every community.

“We will also recruit an additional 8,500 mental health workers for children and adults to reduce delays and provide faster treatment.”