The Government is considering whether to ban adverts for junk food from appearing online and on TV before 9pm.
So far, ads for food and drink that are classed as being high in fat, salt or sugar are only forbidden in or on any dedicated children’s media – for example TV channels specifically for children.
Officials want the public and other affected groups to comment on the plans for the new watershed.
It is part of a range of measures to combat the growing obesity crisis.
One in three children now leaves primary school overweight or obese and the number of children deemed seriously obese is at a record high.
The Department of Health and Social Care (DHSC) said the proposed pre-9pm ban would affect TV programmes, online streaming sites and social media companies.
It comes after broadcasting regulator Ofcom found that youngsters spend 64% of their TV viewing time watching shows not aimed specifically at them.
It also reflects changing viewing habits with further Ofcom research finding children are increasingly watching videos, TV programmes and films on their own devices, often on-demand, rather than on a dedicated TV channel with parental supervision.
Campaigners welcomed the announcement.
TV chef Jamie Oliver said: “If we don’t find effective ways to improve our kids’ health, UK children will live shorter lives than their parents.
“It’s a fact that kids are hugely influenced by junk food ads – so the media and the food industry has a real opportunity here to do something about it.”
Public Health Minister Steve Brine said: “The NHS is already preparing to treat more and more children for the serious effects of extreme obesity in the future, so we have a duty to address the underlying causes because we believe passionately in our NHS.”
The DHSC has previously called obesity a “rising epidemic”, with rising numbers of youngsters becoming affected by related problems like diabetes and asthma.
Professor Russell Viner, president of the Royal College of Paediatrics and Child Health, said he wanted the watershed “implemented as soon as possible”.
Charity Cancer Research UK said watching one extra junk food advert a week, beyond the average of six, led to children eating an extra 18,000 calories a year.