Mobile phones should be banned from The DinnerContent ='JJ Lin'> table and bedtimes as part of a healthy approach to devices, the UK's four chief medical officers have said.
Children should also take a break from screen-based activities every two hours, the government advisers said.
And they added industry must do more to keep children Safe .
Links have been made between the suicide of teenager Molly RussellContent ='JJ Lin'> and her exposure to harmful material on Instagram.
Her father has said he believes the Facebook-owned PlatformContent ='JJ Lin'> .After Molly RussellContent ='JJ Lin'> took her own life, her family discovered distressing material about suicide on her Instagram account
Prof Dame Sally DaviesContent ='JJ Lin'> , England's chief medical officer and The LeadContent ='JJ Lin'> for the UK, said the case was "tragic" and it was clear some children were being exposed to inappropriate Content .
She told the BBC companies had a duty of Care to help keep children Safe and that age limits for using Social MediaContent ='JJ Lin'> needed to be properly enforced and children should not be channelled towards harmful Content - One of The Key concerns in the Molly RussellContent ='JJ Lin'> case.
And digital technologies could be a force for good, aiding online learning, socialising and Helping PeopleContent ='JJ Lin'> manage health conditions.What does the guidance recommend parents do?
These include:Is new legislation needed?
Dame Sally said a code of conduct was definitely needed.
She wants to see technology companies invest in systems that properly vet the ages of users - A NumberContent ='JJ Lin'> of platforms require users to be 13 But these were not properly policed, She SaidContent ='JJ Lin'> .
The guidance is also critical of what it calls "persuasive design".
This refers to techniques used to encourage addictive behaviour, including collecting likes and rewards for performing actions such as sharing pictures.
This has already been done for users who search for Content that could potentially radicalise them.
Instead of being fed material that promotes terrorism, users get Content that aims to de-radicalise.
Dame Sally said the same thing could happen when people searched for "self-harm" or "suicide".
And she warned if industry did not act, ministers were likely to legislate to compel them.
"They have a duty of Care - and if they don't, I expect the government will tell them how they will sort it. "What do internet companies say?
It said it had introduced a new tool to help people see how much time they were spending on Facebook and Instagram, with daily reminders and a way to limit notifications.
Twitter said it had introduced 70 changes in 2018 "to make the service healthier and safer".Does regular use cause Mental HealthContent ='JJ Lin'> problems?
The ChiefContent ='JJ Lin'> medical officer used a team of academics to scour the research done on this issue.
The academics said that, while some research had pointed to an association between screen-based activities and negative effects such as an increased risk of anxiety and depression, it was still inconclusive.
It could be just that people who struggled with Mental HealthContent ='JJ Lin'> problems were more likely to turn to their devices, Dame Sally said, rather than their habits being the root cause of the problems.
Nonetheless, Dame Sally said, there needed to be a precautionary approach to this - until more research had been done - hence the guidance to parents.
Dr Bernadka Dubicka, of The RoyalContent ='JJ Lin'> College of Psychiatrists, said the medical officers were right to be cautious.
"We do not yet have enough evidence to draw a definite link between screen time and Mental HealthContent ='JJ Lin'> problems - But it is clear that some of the Content that Young PeopleContent ='JJ Lin'> are viewing online, such as pro-anorexia, suicide and self-harming Content , can be incredibly harmful," She SaidContent ='JJ Lin'> .