LONDON (AdAge.com) -- The debate on junk-food advertising and its link to childhood obesity has stepped up in Europe, particularly in the U.K. and France. A U.K. ban on TV junk-food ads targeted at kids younger than 16 will take effect July 1, ending the broadcast debate and shifting the spotlight to other media.

Mars, which attracted global publicity last month when it announced it would stop advertising to kids under 12 in the U.K., will in fact have no choice in the matter, and must accept further restrictions on communications to kids under 16.

Print, posters, online (except corporate websites) and cinema ads must fall in line with the broadcast rules. But because nonbroadcast media are regulated by a separate body, the arguments over marketers' responsibilities are being raised all over again.

The Committee on Advertising Practice -- the ad industry's self-regulatory body responsible for nonbroadcast media -- is finding it tough to agree on how closely to follow the rules set for TV by government watchdog Ofcom.

Outwardly, CAP is committed to applying Ofcom's rules. Inside the group, disagreement over the government's definition of unhealthful food is building into a rebellion against the broadcast code.

The advertisers' association, the Institute of Practitioners in Advertising, has already spoken out against the government's "nutrient-profiling scheme," which categorizes food as high in fat, salt or sugar. That means Marmite (a spread full of Vitamin B), along with avocados, cheese and raisins, cannot be advertised to under-16s. But French fries, diet cola and chicken nuggets all pass the test.

"The big issue is nutritional profiling," one CAP member said. "The system is totally flawed and the debate is heated." CAP can choose to create its own definition of junk food, and the committee, made up of different trade associations, is considering this option.

System in trouble?
However, U.K. Health Minister Caroline Flint has made a thinly veiled threat of legal action if Ofcom's junk-food TV-ad rules are not applied to nonbroadcast media. She said in a statement, "We now look to [CAP] to put in place similar rules for other media such as cinema, magazines and the internet." Otherwise, the whole self-regulatory system could be in trouble.

"The Ofcom intervention is disproportionate," said Stephan Loerke, managing director of the Brussels-based World Federation of Advertisers. "Nowhere else is there such a heavy intervention with scheduling."

Across Europe, debate rages over how to deal with growing childhood obesity and the role of marketing. In Sweden and Norway, a ban on TV advertising to children under 12 hasn't changed the trend toward obesity.

The French government has come up with its own controversial solution. Starting this month, all junk-food ads in France must devote 7% of space to health messages about a balanced lifestyle, exercise and eating fruits and vegetables.

In France, junk food is defined as any processed food. "There are huge legal uncertainties yet there is no transition period," Mr. Loerke said. "Does the law extend to corporate websites? How do you measure 7% of the space? Is mineral water processed if the bubbles are artificial? It's incredibly complex."

French marketers can drop the health messages and instead donate 1.5% of the campaign budget to a fund for government health campaigns. But marketers are reluctant to subject themselves to what they see as an additional tax.

Still ahead: The European Union's legislation, called the Audio Visual Media Services Directive, will impose rules and definitions later this year, probably extending reach to cellphones, and ensuring European governments are constantly re-evaluating restrictions.