Children are being targeted by ads for foods high in fat, sugar and salt

The Food Commission said billions of dollars a year were spent globally on marketing foods high in sugar, salt and fat.

The adverts, mainly on television and sometimes targeted at children as young as two, were eclipsing any messages given to children about healthy eating, it said.

Kath Dalmeny from the commission told BBC News: "Unfortunately the kinds of foods that attract the biggest advertising budgets are the fattiest, and sugariest, and saltiest.

"Those are just the things that children should be eating less of, not more of...

"These are the ones that are advertised on children's television, to children, saying these are great exciting, fun things that will improve your performance."

She said parents could not necessarily be blamed because they had no way of telling from the adverts that some cereals, for instance, were 40 or 50% sugar.

Junk food and sugary drinks are supported by enormous advertising budgets that dwarf any attempt to educate children about healthy diets Food Commission

The commission urged the World Health Organisation to consider banning adverts for "energy-dense, low-nutrient" food aimed at children.

It said the marketing of such food and drink in schools should be outlawed.

All TV adverts for food should be pre-vetted, it said.

There should be publicly-funded incentives for food companies to improve the nutritional content of their products.

The commission also expressed alarm at the way advertising was being aimed at children with techniques such as websites and link-ups with films.

Food industry fights back

But the food industry said its adverts were responsible.

The Food and Drink Federation, a trade body representing manufacturers in the UK, said: "UK food and drink manufacturers take a very responsible view of their relationships with children.

"There are already strict codes of practice governing advertising.

"These state that ads should not encourage children to eat or drink frequently throughout the day, condone excessive consumption, or suggest that confectionery or snacks should replace balanced meals."

The WHO estimates more than a billion adults worldwide are overweight and at least 300 million of these are clinically obese.

It is currently working on a strategy for improving diets through healthy eating and physical activity.