Giant food companies such as Coca-Cola and McDonald's were accused yesterday of exploiting the name of the Prince of Wales as a front for a campaign which will promote exercise as the cure for obesity, rather than changes in diet.

The International Business Leaders Forum (IBLF), which was set up more than 20 years ago by Prince Charles and of which he is president, has recently launched a healthy eating, active living global partnership (Heal).

Among the companies involved are Coca-Cola, PepsiCo, Cadbury Schweppes, McDonald's, Kraft Foods and Nestlé as well as sportswear, hotels and leisure groups.

But campaigners say some of these companies have lobbied against a World Health Organisation global strategy document which identifies the fats and sugars in fast and processed food as a major cause of obesity.

The Heal partnership will hold a meeting in Geneva on Thursday, during the WHO's world health assembly, which will be considering the strategy. It is understood that a number of organisations have refused to attend the Heal event, including the WHO, the National Diabetes Federation and the International Obesity Task Force.

Gary Ruskin, executive director of the campaign group Commercial Alert in the United States, is concerned about the status the prince's name will give the food companies.

"Why is the heir to Britain's throne lending his good name to this organisation, which seems to be acting as a front for junk food and soft drink companies?" he said.

"If the IBLF were serious about social responsibility, it would tell junk food companies to improve public health by halting advertising to children, removing their products from the schools, and ceasing to maximise their profits regardless of the impact on public health."

Tim Lang, professor of food policy at City University in London, also had concerns. He says he respects the Prince of Wales Foundation, which at tempts to encourage progressive forces within the business community. But the stakes are high for the food industry, which is facing the prospect of radical changes in dairy farming, meat production and other areas if countries are to reduce dietary fat intakes as the WHO recommends.

"I get very nervous if well-meaning people start allowing their names to be used, without necessarily realising it, in a strategy that benefits the least progressive, most reprehensible elements of the food industry," he said. "We have a public health crisis of immense proportions ... I would say to the IBLF, either keep out of this because you will get caught up in the crossfire, or side with the medical facts."

Critics said Heal was modelled on an American initiative with a similar name, the Public Partnership for Healthy Eating and Active Living, which has launched a strategy called America on the Move. The sponsors of America on the Move are PepsiCo, Cargill and Masterfoods USA. Other backers include Kelloggs, Kraft and Coca-Cola.

America on the Move talks of "energy balance" - the theory that what you eat does not matter as long as you burn up the energy you consume.

"The message is simple: move more and eat less," says the website. "Making two small daily changes is all it takes. By taking an extra 2,000 steps (the equivalent of about one mile) and eating only 100 fewer calories on a daily basis, individuals can prevent weight gain ..."

Mike Jacobson, of the Washington-based Centre for Science in the Public Interest, said there were a number of such industry-backed programmes designed to distract attention from unhealthy food. "They enable industry to say we're doing something, and then politicians who don't want to take stronger actions can say, well, industry is doing plenty - let's see how it works out."

Olive Boles, of the IBLF, who is working on the Heal partnership, said the purpose was to encourage businesses to get involved in tackling obesity, whether in their own workforces or by contributing to public health more generally. She denied Heal was about exercise rather than diet.

"Our view is ... about taking a balanced approach. It is diet and exercise and lots of other things as well," she said.

"We are not a lobbying organisation. Our view is that obesity is an issue in any event. We are trying to mobilise business. We're exploring what good practice is out there and how it can be built upon."