Ministers threatened yesterday to clamp down on food manufacturers who lace products with salt after the food standards watchdog warned that child obesity could cut life expectancy in Britain for the first time in more than a century.

Ministers threatened yesterday to clamp down on food manufacturers who lace products with salt after the food standards watchdog warned that child obesity could cut life expectancy in Britain for the first time in more than a century.

The Government is to issue an ultimatum to food companies that they will be forced to display prominent health warnings on high-salt products if they fail to sign up to targets for cutting salt within three months.

The move came after Sir John Krebs, chairman of the Food Standards Agency, warned that obesity was "a public health time bomb" which could mean that today's children enjoy shorter lives than their parents. Sir John told The Observer: "We're all looking forward to a longer and healthier old age, and that trend could be reversed. Doing nothing is not an option.

"Obesity carries very significant health risks. Increased heart disease, type II diabetes, which is now beginning to appear in children for the first time, and certain kinds of cancer are linked with obesity."

The agency is calling for a reduction in salt, sugar and fat levels in children's food, curbs on the amount of advertising for sweets, crisps and snacks during children's television programmes and a ban on "celebrity endorsements" of such products and the sponsorship of pop concerts and sporting events by the companies which make them. This proposal could prevent Gary Lineker appearing in adverts for Walkers crisps and stop Pepsi-Cola sponsoring the England football team and concerts by Britney Spears.

The Department of Health summoned supermarket chains and food producers to a meeting tomorrow after new research showed that salt kills 35,000 people every year.

Researchers believe high levels of salt in processed food, such as bacon, bread, crisps and some breakfast cereals, contribute to increasing levels of high blood pressure, strokes and heart attacks which kill tens of thousands of people each year. Hidden salt in processed food is estimated to make up 80 per cent of people's daily intake.

Melanie Johnson, the Public Health minister, warned that products would be forced to carry "high in salt" labels unless manufacturers came into line. She said: "Salt can be a hidden killer. Whereas people are generally aware of the risks of a high sugar or high fat diet, they're often unaware of the effect of high salt intake.

"But there's only so much consumers can do. What many people consider a health- conscious diet is often high in salt. Three quarters of salt intake comes from processed foods, like ready meals, where there is little choice."

Britons' average salt intake has increased to nearly twice the recommended daily level since the 1980s, according to the Department of Health.

Men eat about a teaspoon of salt more than the recommended amount each day. On average, women consume almost half a teaspoon more than they should. Surveys show that intake increased from about 10.1 grams per day for men and 7.7 grams per day for women in 1986-87 to 11 grams per day for men and 8.1 grams per day for women in 2000-01. Government advisers want to cut daily consumption to about 6 grams.

Professor Graham MacGregor, a leading expert on the effect of salt on blood pressure levels, called for an immediate reduction of 10 to 20 per cent of salt in all food.

Professor MacGregor, whose department at St George's Hospital in Tooting, south London, has pioneered work to reduce high blood pressure by cutting salt in patients' diets, said salt in food could be responsible for 70,000 strokes and heart attacks and 35,000 deaths each year. He said bread was the major source of salt in diets and could contribute to a quarter of people's daily intake. "The onus is on the food manufacturers. They are killing people and they need to start taking the salt out. They are responsible for these deaths," he said.

"An immediate cut of 10 per cent by the food industry would reduce salt intake in the UK population on average by 1 gram per day per person and save 5,800 lives over the next year - 16 people every day of the year. Furthermore, there would be an almost equal reduction in the number of individuals having a heart attack or stroke and surviving. Stroke is the leading cause of disability in the UK."

The Food and Drink Federation, which represents the food industry, insisted that action was being taken to cut salt in food. A spokeswoman said salt in breakfast cereals had been cut by 16 per cent in the past five years, while manufacturers were committed to a 10 per cent reduction in salt in soups and sauces each year until 2005. Sainsbury's joined the drive this weekend by announcing cuts in salt in five key types of processed foods.

Celebrities sell

CADBURY'S: The company's 6 per cent rise in UK sweets sales last year was attributed to its successful sponsorship of the Commonwealth Games. A separate £9m campaign, endorsed by Paula Radcliffe and Audley Harrison, was criticised for encouraging children to buy chocolate bars in return for new sports equipment.

McDONALD'S:< Justin Timberlake recently signed a multimillion-pound deal with McDonald's only months after the fast-food company, which spent £42m on advertising last year, announced its first loss since 1965. Sales in the US slumped last year.

MULLER YOGHURT: More than 125 million pots a year of Muller Corner yogurt were sold after a £5m advertising campaign featuring Joanna Lumley. The German company has continued to increase its UK market share.

HEINZ SALAD CREAM: Relaunched three years ago with the endorsement of Denise Van Outen and Graham Norton, it has experienced an unexpected comeback and maintains a 59 per cent market share.

NESTLE: The company's controversial promotion of powdered milk for babies in developing countries meant its £6m Pop Idol deal was condemned by some campaigners. Germaine Greer and Jim Crace refused to attend the Hay-on-Wye literary festival last year.