While falling short of calling for ''plain packaging'' on sugary and fatty foods, the Obesity Policy Coalition said the federal government should ban marketers from using cartoon characters and giveaway toys to promote junk and unhealthy foods.

A coalition spokesman, Professor Boyd Swinburn, said cartoon characters were the common factor used to draw children to fattening foods and drinks but companies were now using free online games, apps, movies and other new media to promote unhealthy food.

''Cartoon characters and toy giveaways are certainly the hook used to draw children in,'' he said.

''It is a huge battle, akin to the battle with tobacco over plain packaging.''

Professor Swinburn said self-regulation had failed because some companies refused to sign up to industry codes and loopholes often allowed companies to escape criticism.

A Deakin University senior lecturer, Paul Harrison, said the food industry had allowed stricter rules on traditional advertising - whose power is on the wane - while developing online games, movies, product give-aways and health sponsorships.

These platforms ''flew under the radar'' of regulators, Dr Harrison said.

In Advances in Communication Research to Reduce Childhood Obesity, released this month, Dr Harrison looked at the integrated marketing campaigns used for Nutri-Grain, Freddo Frogs and McDonald's Happy Meals and how they appealed to children.

He said marketers often cleverly used no logos to avoid criticism, but instead used characters and colours associated with their products.

''Children are not stupid. They can work out the association between a character and a product from a very young age, even if they are not together at the time,'' he said.

On one website children were encouraged to create an avatar to interact with Freddo Frog, to play games, do puzzles and other activities. The company also used child-size displays in stores, Christmas stockings, party cakes and chocolate fundraising drives through schools and childcare centres.

Other examples included a free DVD giveaway featuring an adventure with the Paddle Pop Lion and Gatorade, which has been allowed to promote ''hydration'' to school children in Victoria.

''These companies try to say that they are not advertising to children, but of course they are,'' Dr Harrison said.

He said advertising regulators and industry codes were failing to keep up with technology and marketing changes. A single authority should look at whether marketing was designed to appeal to children regardless of the medium, he said.

The spokesman for the Australian Food and Grocery Council said increased regulation overseas had not reduced childhood obesity, but ''there is a need for more positive, creative and collaborative approaches that will actually work, rather than blanket bans''.

He said the council had initiated the Healthier Australia Commitment to help reduce the incidence of chronic preventable diseases.