From July 2017, ads for HFSS food and drinks will be banned in children's media – including YouTube channels directed at children, children's cinema, children's magazines, internet and app games targeted at children – and those media aimed at adults and families where children constitute a significant minority – at least 25% – of the total audience.
"Our rules will eliminate high-sugar products ads from children's media and media where adults comprise up to 75% of the audience," Shahriar Coupal, a director of the Committee of Advertising Practice, told the BBC.
"We don't think it's justified to push that figure up to 90% or to ban these ads entirely," he added. "We have to balance the need for protection with freedom of expression."
Campaigners welcomed the moves but argued that many children would still be exposed to HFSS advertising through popular TV programming like The X Factor and Britain's Got Talent and that there should be no HFSS advertising on TV before 9pm.
Malcolm Clark, campaign co-ordinator for the Children's Food Campaign, drew attention to the potential loophole of the 25% rule, pointing out that information about the composition of online and social media audiences was not readily available.
"Just as many of the TV programmes most watched by children aren't covered by the rules, so it looks like many of the most popular social media sites won't be either; nor will product packaging itself," he said.
The Food and Drink Federation, while opposed to the idea of a sugar tax, backed the tighter restrictions on advertising. "As young people move away from traditional media towards new and social media, we feel it's important that ad rules keep up with this change," said chief executive, Ian Wright.
That stance was echoed by the advertising industry itself. "Regulation is important," said Advertising Association chief executive, Stephen Woodford, adding: "but we also know the effects of advertising are relatively small, so whether it's supporting parents with healthier choices, improving education or getting more people, more active, let's now grab the opportunity to put our collective energy into tackling the big drivers of obesity."
A technical fix is also an option: Nestlé recently claimed it could reduce sugar content in its products by as much as 40% by altering the structure of sugar crystals.
Data sourced from BBC, Financial Times, Campaign; additional content by Warc staff