These include changes in the way sites are structured to “remove addictive capabilities” which encourage users to get hooked.
This could mean getting rid of functions like “auto-play” which mean content is continuously delivered, or pushed with nudges that “you might like” particular videos or games, and praise for logging in regularly.
Other measures include effective age verification methods, age-appropriate advertisments, and the removal of harmful content such as bullying or images of self-harming.
And the technology industry will be asked to contribute to funding on research on the impact of screen time, and to share anonymised data to improve the scientific evidence base about the potential risks and benefits of social media.
Shirley Cramer, chief executive of the Royal Society for Public Health said the advice would help parents who were “crying out for help to protect their children and help them navigate the Wild West of the digital world.”
Dr Bernadka Dubicka, from the Royal College of Psychiatrists said: “The chief medical officer is right to be cautious about how long children are spending looking at screens rather than talking to their friends or getting a good night’s sleep.
“We do not yet have enough evidence to draw a definite causal link between amount of screen time use and mental health problems but it is clear that some of the content that young people are viewing online, such as pro-anorexia, suicide or self-harming content, can be incredibly harmful.”