Manufacturers dispute the claims
Manufacturers are making misleading claims about fatty and sugary foods aimed at children, a report says.
The British Heart Foundation said ads for brands including Kellogg's, Dairylea and Nestle gave a "wholesome" image for unhealthy products.
It called for tougher government regulations on food marketing.
The Food and Drink Federation, which represents manufacturers, branded the claims "nonsense", saying advertising was already tightly controlled.
The report was prepared by the Food Commission, a body which campaigns for better food, and looked at the advertising of children's breakfast and lunchbox foods.
It suggested that companies used a variety of "misleading" techniques to make them seem healthier than they actually are.
One example it gave was Kellogg's "Coco Pops" Cereal Bars, which are marketed as the "best choice for a lunchbox treat".
Images of grapes and wholemeal bread are used on the packaging, and the adult rather than the child guideline amounts of sugar are printed, which could confuse parents, said the report.
Packaging for the cheese product Dairylea said it had "no artificial colours, flavours or preservatives", but the report said that just one portion had nearly a third of a child's recommended daily saturated fat intake.
Also singled out for criticism was Nestle, with a promotion for their cereals and "magic straws" describing their benefits for children's bones, but not the fact that more than half of the weight of a "magic straw" is sugar.
British Heart Foundation chief executive Peter Hollins suggested firms were exploiting "legal loopholes" to market products to children.
He said: "It's clear that some food companies are preying on parents' concerns to actively market children's food that is high in sugar, salt and fat.
"We are calling on the UK government to rigorously limit the marketing of unhealthy foods and make sure labels are clear and consistent."
A spokesman for the Department of Health said: "There are now fewer ads on TV that are tempting our children into bad eating habits - but we must continue to keep our eye on other types of media.
"We must do more to reduce marketing unhealthy foods to children elsewhere - and that includes kids promotions on the internet, at the cinema, in magazines.
"Ofcom is reviewing the current restrictions and will report its findings shortly."
However, Julian Hunt, from the Food and Drink Federation, described the report as a "dodgy dossier" and insisted that regulations were being followed.
"When it comes to the marketing of food and drink products, we know that the UK is one of the most strictly regulated countries in Europe.
"It is complete nonsense to suggest that manufacturers are exploiting legal loopholes in the marketing regulations - a report published by the Advertising Standards Authority only this week shows that 99% of advertising in all media is fully compliant with the rules now in place.
"It is also highly spurious to allege that nutrition and health claims are not regulated; they are, thanks to a strict EU regulation covering all nutrition and health claims on food and drink products."
'No rules broken'
The manufacturers themselves said clear information about "guideline daily amounts" was carried on packs.
A spokesman for Nestle said: "None of the marketing techniques listed in the report are in breach of current UK and European marketing and advertising rules."
Kellogg's described the suggestion they were exploiting regulatory loopholes as "rubbish", adding: "Our on-pack claims are rigorous and all our marketing reflects the latest advertising codes."
Kraft, the makers of Dairylea, said the amount of fat in a portion was actually 16%, rather than a third.
A spokesman said: "Parents tell us that no artificial ingredients are important to them, so that's what we highlight."