The government should force food companies to reduce the size of bumper portions, says a British health expert.

Making ice creams, chocolate bars and other processed foods 20% smaller could help stem the tide of heart disease, says Dr Malcolm Law.

Extra-large packs and two-for-one offers tempt consumers, including children, into over-indulgence, he believes.

A code of conduct between the government and the food industry would have "a large public health impact", he says.

"It is important that the nation changes its diet," said Dr Law, an epidemiologist at London's Wolfson Institute of Preventative Medicine.

"Health education and health promotion is fine but I think the response to date has been disappointing," he told a conference at the Royal Society of Medicine.

"I would like to seriously propose that negotiation between the government and the food industry to change the food supply might at least have some limited success."

Fat attack

Dr Law says the government should initiate talks with food manufacturers in a similar way to past agreements with the tobacco industry.

We are still not eating enough fruit and veg

Research suggests people tend to finish their plates no matter how much food is served.

Most do not feel hungry when given a smaller portion and benefit from a lower fat diet.

Other possible measures proposed by Dr Law include removing the financial incentive to buy large servings of food, for example buy-one-get-one free offers.

Reducing fat content in the food supply, such as frying chips in vegetable oil not lard, could also improve the nation's health.

Farm-to-fork

Professor Christine Williams of the University of Reading says an integrated food policy involving manufacturers and agriculture is needed to meet government targets on heart disease and obesity.

She also called for new measures to help consumers understand how much fat was going into processed food.

"It is very complex for consumers to understand the type of fat and amount of fat because of the packaging," she said.