The heads of McDonald's, Cadbury Schweppes and Pepsi said yesterday that their products were not to blame for Britain's obesity epidemic.

The chief executives of the three companies claimed that heavy marketing of junk food, "super size" portions and offers of promotional toys had little effect on what most people ate.

Andrew Cosslett, the managing director of Cadbury Schweppes, said: "There is no correlation between confectionery consumption and obesity. All the evidence suggests that people eat our products extremely sensibly.

"The problem is that people are buying things that they think are low-fat, products that are masquerading as healthy with misleading labels." Mr Cosslett claimed that products such as low-fat yoghurts were more to blame for the rising rate of obesity than sweets. "There is nothing dangerous about a Curly Wurly," he said.

He and the heads of Britain's other leading food companies were giving evidence to the House of Commons Health Select Committee investigation into obesity.

The committee is considering whether to recommend a ban on television advertising of high-fat and sugary foods during children's viewing times, and the introduction of cigarette-style health warnings on junk food. One in five people in Britain is classed as overweight or obese and rates have tripled among children.

Campaigners say the aggressive marketing of sweets, crisps and soft drinks, using sporting heroes such as Gary Lineker for Walkers crisps and cartoon characters for McDonald's Happy Meals, encourages people to eat poor diets. Increased portion sizes, such as "go large" burger meals and extra large chocolate bars, have also been blamed.

But the heads of the three companies rejected these claims. Mr Cosslett said surveys by Cadbury Schweppes showed that obese people ate less confectionery than the general population.

Julian Hilton-Johnson, the vice-president of McDonald's in the UK, dismissed a suggestion that health warnings should be displayed on burgers, or that staff should deter obese customers from buying extra-large meals. "I don't think it is for us to presume to tell our customers what they should be eating," he said. Mr Hilton-Johnson claimed that super-size meals accounted for 3 per cent of McDonald's sales and that the company offered healthy salads, fruit with Happy Meals and organic, semi-skimmed milk.

Martin Glenn, president of PepsiCo UK, said: "We are confident from talking with our consumers that most parents understand they should be accountable for the healthy lifestyle of their children and thanks heavens most do."

All three heads insisted that advertising and promotions had not led to increased sales, but merely encouraged people to switch brands.

The Health Select Committee will publish its recommendations early next year.