The government is to produce the first official guidelines on the maximum amount of time young people should spend on social media, health secretary Matt Hancock says today, amid growing concern about the links between its excessive use and mental health problems among children.

In an interview with the Observer before the Conservatve party conference, which opens this weekend in Birmingham, Hancock says he has instructed the UK’s chief medical officer, Dame Sally Davies, to draw up advice as soon as possible that he hopes will become an accepted “norm in society”, like that on recommended maximum alcohol consumption for adults.

Hancock, who has three children under 12, says he is seriously alarmed by evidence of links between mental health problems in young people and unlimited social media use.

He suggests that turning off phones at night when children go to bed would be one “absolutely standard, straightforward way of limiting the damage”.

He said: “I am, as a father, very worried about the growing evidence of the impact of social media on children’s mental health.

“Unrestricted use [of social media] by younger children risks being very damaging to their mental health. So I have asked the chief medical officer to bring forward formal guidance on its use by children.” This would, he believes, “empower” parents and teachers as they struggle to enforce sensible limits and explain them to children. “As a parent you want to be able to say, ‘the rules say you shouldn’t use social media for more than a certain period of time’. This is why we have a chief medical officer: to set a norm in society, make judgments on behalf of society, so that individual schools or individual parents don’t have to decide.”

He also wants Davies to bring forward guidance on the minimum ages at which young people should be able to use certain sites. Many big social media companies issued advice but did nothing to enforce it, he said.

“The terms of reference of Facebook and Instagram say you shouldn’t be on it if you are under the age of 13. But they do nothing to police that. The guidelines for WhatsApp say you shouldn’t be on it unless you’re 16. But again, they don’t lift a finger.”

Concern is also growing in government and medical circles about the effect of “recreational” screen use on children’s ability to learn and acquire knowledge. A study published last week in the Lancet Child & Adolescent Health, based on a survey of children in the US, found higher levels of cognition in children whose “recreational screen time” was less than two hours a day.

A separate US study of people aged 18 to 24 found last year that 41% of social media users thought it made them feel sad, anxious, or depressed.

A report for Ofcom last year found that children aged between five and 15 in Britain spent an average of 15 hours a week online and half of 12-year-olds had a social media profile.

In academic circles, debate continues over whether social media has more negative than positive effects.

A report last year by the Education Policy Institute found a link between social media use and mental health issues. It cited figures showing that while 12% of children who spent no time on social media had symptoms of mental ill health, the figure rose to 27% for those who were on the sites for more than three hours a day.

The use of mobile technologies such as smartphones had, it said, also been linked to anxieties about conforming with social norms and the need for “likes” – external validation of personal content posted online.

However it concluded that because young people were increasingly conducting their lives online, it would probably be “futile” to attempt to protect children and young people from all online risks.

“This indicates that the focus of public policy should be on how to develop resilience in young people to maintain their emotional and mental wellbeing and live safe digital lives.”

Some tech companies have recognised that parents need control over how much time their children are spending online. Apple has introduced a new “screen time” feature that allows parents to restrict the amount of time children spend in front of their screens online. Facebook recently introduced a number of new tools to help users manage their time on Facebook and Instagram.

These include an activity dashboard showing average time spent on each app, a daily reminder to give users an alert when they have reached the amount of time they want to spend on that app, and a new way to limit notifications.