This autumn the Department of Health will announce measures to reverse a doubling of the problem in the past decade. More than a fifth of the population is now considered overweight, costing the NHS an estimated ??500m a year and the wider economy about ??2 billion in related illnesses and time off work.

Ministers are understood to be considering warnings on unhealthy foods, setting up ??safe routes?? so children can walk or cycle to school, and banning supermarket promotions of fat-laden products.

However, the most controversial measure is likely to be a proposed ban on advertising during children??s programmes. Almost half of children??s adverts are for cakes and sweets, and studies show that more than 90% of food advertising during children??s broadcasts is for foods high in fat, salt and sugar.

Sir Liam Donaldson, the chief medical officer, said: ??Action is needed to help and support people, particularly children, to reshape their diet. There is a case for adopting the precautionary principle for the marketing of foods to children.??

Officials are expected to ask food companies to promote more healthy products and reduce pack sizes. Tesco has sold 300% more apples to girls by introducing ??Barbie-style?? packaging.

The measures will be accompanied by a public education campaign likely to involve television advertising, and a new approach by teachers. Professor Sue Fairweather-Tait of the Institute of Food Research said: ??We have a pretty good idea what a healthy diet consists of and the big question is how you get consumers to follow it.??

The food industry said an advertising ban would not be helpful. "Children are media savvy. Marketing to them is a legitimate activity," said the Food and Drink Federation.

Additional reporting: Claire Newell

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