The move follows concern about the substances — known as hydrogenated vegetable fats — which have been linked with heart disease, narrowing of blood vessels and diabetes.

Hydrogenated fats are believed to pose a significantly higher health risk than naturally occurring fats.

In Britain, the fats are widely used in biscuits, cakes, pastry, margarine and ready meals. The fast-food industry also makes wide use of hydrogenated oils for frying. There is no obligation to declare the fats on labels.

In America, many food companies have announced they are to stop using such fats. The US government has ordered companies to detail such fats on food packaging.

The Food Standards Agency in Britain is considering a similar move, informing food manufacturers and retailers that they may soon be required to label all foods containing the fats.

The agency said: “These fats can raise blood cholesterol levels and increase the risk of coronary heart disease.”

Of the 5,000 food lines sold by Marks & Spencer, 1,200 were, until recently, made with hydrogenated vegetable fats. By the end of this month, that should have been cut to about 700.

Guy Farrant, director of food at Marks & Spencer, said: “We have removed hydrogenated vegetable fats from our ready meals and we are now working to remove them from all our food products by mid-2006.”

The fats are made by heating natural fats such as soya or palm oil to more than 250C and then bubbling hydrogen through them.

This turns the oil from a liquid to a dense waxy tasteless solid that improves texture, binds food particles together and prolongs food’s shelf life.

However, research has shown that hydrogenated fats shorten human life. The main problem lies with a sub-set of fats formed during hydrogenation known as trans fats.

Studies link these fats with raised cholesterol and narrowing of blood vessels, increasing the risk of heart attack and stroke. They also make the body resistant to insulin, raising the risk of diabetes.

Tim Lang, professor of food policy at City University, London, welcomed Marks & Spencer’s decision. He said: “Why has it taken so long? Hydrogenated vegetable fats are uniquely bad for consumers in every way.”

Tesco and Waitrose have also promised to cut the use of such fats in own-brand food.

Jane Landon, associate director of the National Heart Forum, said the key question was what Marks & Spencer would use instead. She said: “They need to avoid replacing them with other forms of harmful fat.”

Explore UK News

• Crime News

• Education News

• Health News

• Science News

• Scotland News

Times Recommends

• Gentleman thief stole pages from rare books
• Picture: the Queen in 1970s flares
• Honoured after 70 years: man who saved thousands