The proposal is one of a number of policy options drawn up by Sir John Krebs, chairman of the Food Standards Agency, to head off what he calls the “ticking timebomb” of rampant childhood obesity.

Krebs warned in an interview last night that, if the number of overweight young people was not reduced, life expectancy could start to fall.

“What we are faced with is a situation where, if nothing is done to stop the trend, for the first time in a hundred years life expectancy will actually go down,” he said.

Britain has some of the highest proportions of overweight young people in the developed world, with 8.5% of six-year-olds and 15% of 15-years-olds classified as obese. It is predicted that by 2010 obesity will cost the NHS about £3.6 billion a year.

Krebs said: “Doing nothing is not an option. We know that the level of obesity in children is rising and this is why the agency is encouraging a wide debate on the options for action that could make a difference.”

After public consultations, Krebs will send his proposals to Tessa Jowell, the culture secretary, early next year. In addition to the possible bans, other measures under consideration include: o Pressurising supermarkets to offer “buy one, get one free” promotions only on healthy children’s foods. oMaking shops replace sweets on sale at checkouts with healthier options. oLabelling products that are high in fat or sugar clearly on the front of the packets, possibly in the form of a government health warning. oBanning vending machines from stocking sweets and crisps in schools and leisure centres. oAllowing token-collecting for schools only on healthy foods, ending schemes in which children collect coupons from snacks or sweets that are redeemed for books or computers for classes.

Krebs may recommend that some of the proposals are enforced by new laws.

Tomorrow the Medical Research Council will add to the calls for action, warning that the prevalence of obesity in young people in Britain has trebled in 20 years, with 4% of 4-18-year-olds now classed as obese and 15% as overweight.

Any curbs on advertising are likely to face accusations of a nannying attitude by the government as well as fierce opposition from the food and marketing industries.

Martin Paterson, deputy director-general of the Food and Drink Federation, said: “Advertising to children is already a very heavy regulated area. The idea of banning things is too simplistic. Parents will take a dim view of nanny state approaches to matters of personal choice.”

A ban on celebrity endorsements would come as a blow to snack manufacturers, who have found such strategies lucrative. Earlier this year Gary Lineker, the former England football captain, was berated by the Food Commission, the UK’s leading independent food watchdog, for promoting Walkers crisps, which like most crisps are high in fat and salt.

A spokeswoman for the Department of Culture, Media and Sport said: “We’re pleased the FSA have joined in the debate and look forward to their final report.”

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