Junk food such as burgers, chips and fizzy drinks, should carry tobacco-style health warnings in a bid to reduce rising obesity rates, a senior Labour MP told fast food bosses today.

Consumers should know how much exercise it would take to burn off the huge number of calories in junk food, said the chairman of the Commons health select committee, David Hinchliffe.

Mr Hinchliffe said the calorie content currently listed on food labels meant little to most members of the public, and called for blunter warnings on junk food.

For example, people should be informed that they would need to take a nine-mile walk in order to burn off the calories in a McDonald's cheeseburger with fries and a milkshake.

He said: "At the moment calorie content does not mean a great deal to people. Perhaps the message is not sufficiently blunt."

Julian Hilton-Johnson, the vice-president of McDonalds Restaurants Ltd, rejected Mr Hinchliffe's comparison between junk food and tobacco, but agreed people should be clearly told what they were eating.

Nutritional information "certainly should be simplified", Mr Hilton-Johnson told MPs. "It is important that whatever message is put out there is well understood."

He was giving evidence with other food industry bosses to the health select committee's investigation into the rising level of obesity in Britain.

Obesity now affects 21% of men and 23% of women in the UK. A further 46% of men and 33% of women are overweight.

Earlier this month, the influential International Obesity Taskforce warned that more than 40% of men and women in the UK could be obese within a generation.

Mr Hilton-Johnson claimed putting toys in children's Happy Meals was not necessarily designed to increase sales.

"When you run a promotion, sometimes you have four or five toys in a set run over a four or five week period," he told the committee.

"The object is not to drive people to come in more often, it is about getting different people to come in more often."

He said it should be parents who had the ultimate choice about what their children ate.

However, several studies - including the book-length investigation "Fast Food Nation" - have shown how fast food restaurants consciously use their multi-million pound advertising budgets to target children.

But Mr Hilton-Johnson admitted they made positive efforts to get customers to buy more by asking whether they wanted bigger portions.

"What we do is offer a range of portion sizes so people can decide what they want."

Andrew Cosslett, managing director of Cadbury Schweppes in Europe, the Middle East and Africa, defended the production of king-sized chocolate bars.

"They were introduced for a very distinct market, for very active people, and they are sold that way," he told the committee.

"They have labels which show the calorific content and they are always sold alongside other products so people can make the choice."

Mr Cosslett rejected the suggestion from MPs that there should be health warnings put on certain products.

"I think health warnings are a dangerous thing and while we understand the problem I don't think a Curly Wurly is dangerous.

"I take exception to the junk food term," he said, adding: "I call bad diets junk diets."

Tim Mobsby, area president for breakfast cereal manufacturer Kellogg's in Europe, repeated the industry's position when asked about the possibility of a ban on advertising products high in sugar, salt and fat to children.

He said such a move would be "impractical and ineffective". It would prevent advertising being used "as a force for good".

Following the hearing, Paul Burstow MP, Liberal Democrat health spokesman and a member of the committee, said: "Food companies selling high fat and high sugar foods cannot escape their responsibilities for the consequences of the food they offer the public.

"Obesity is a complex problem. It's down to both what we eat and how much exercise we take.

"For food companies to duck the question of how much a burger and fries or can of coke fits into a balanced diet is letting their customers down."

Walkers have run a campaign which has given away seven million books to schools. But Mr Burstow claimed that 1.2bn packets of crisps needed to have been eaten to hit the target.

"For a company to claim to be socially responsible but then use a 'free books' campaign as a way of selling its products must call that claim into question," he said.