Unhealthy food is being targeted at children via social media and web games by firms avoiding strict TV rules, says the Children's Food Campaign, which calls for action from the advertising watchdog.
A "super complaint" is being lodged over the increasing use of social media and online games to promote junk food to children.
It raises concerns over brand characters, animations, games, competitions and videos which "clearly target children" with food products which are high in sugars, fat and salt.
Malcolm Clark, a spokesman for CFC, told Channel 4 News: "We're talking about colourful, child-friendly games aimed at under-16s - making the product more appealing to children."
He referred to a test case which found advertisers using Facebook games to market food, such as sweets and crisps, to young audiences.
It's an epidemic and it's not getting any better. Malcolm Clark
But he added: "These aren't really individual complaints, it's a whole practice. It's an epidemic and it's not getting any better."
None of the products being criticised can be promoted during children's television programmes because of Ofcom rules to protect children from junk food advertising. However because of a loophole in advertising regulations, companies are allowed to market freely via the internet.
The campaign urges the ASA to uphold its existing code which says "marketing communications must not condone or encourage poor nutritional habits or an unhealthy lifestyle in children". Mr Clark said the standards expected on TV should be matched online.
"Sadly obesity rates are still very high. Education campaigns are all good and necessary, but you need more than that," he said.
"The food environment that children find themselves in - at school and at home - is influenced by advertising.
"At the very least we must ensure the ASA is upholding its existing rules."