The Drug Safety Research Unit in Southampton found that another 300 young women are suffering non-fatal heart attacks that are linked to smoking.

The researchers say that all the heart attacks could have been prevented if the women had given up smoking.

Heart disease is not usually a problem among pre-menopausal women.

The researchers, led by Dr Nick Dunn, analysed 448 cases of heart attacks occurring in British women aged 16 to 44 between October 1993 and October 1995.

The data, collected for a study called the British MICA (Myocardial Infarction Causality), was compared with that of 1,728 women of the same age who had not suffered a heart attack.

The researchers found:

• The more cigarettes smoked on a daily basis, the greater the risk of a heart attack.

• Even in light smokers, who had up to five cigarettes a day, the risk was doubled.

• Smokers of one pack of 20 or more a day were at 25 more risk than non-smokers.

• For smokers of two packs or more a day, the risk increased by a factor of almost 75.

Other underlying conditions such as high blood pressure, diabetes or high levels of cholesterol, further increased the chances of having a heart attack.

Smokers of between one and 19 cigarettes a day, with one other clinical condition, were eight times more likely to have a heart attack than a non-smoker with the same clinical condition.

Writing in the journal Heart, the researchers concluded that 400 women a year would avoid heart attacks if they stopped smoking - and 112 lives would be saved.

They said heavy smokers with other risk factors such as high blood pressure and diabetes were particularly at risk.

The study found no evidence that the contraceptive pill increased a smoker's heart attack risk.

This was thought to be because modern oral contraceptives contain relatively low levels of the hormone oestrogen.

Truly shocking findings

Amanda Sandford, research manager at Action against Smoking and Health (ASH) said the death toll was "truly shocking".

She said: "There is a common misconception among young people that smoking causes disease only in old people. This research demolishes that myth.

"It also shows that even light smokers are conning themselves if they think they are not at risk."

She said the findings underlined the need for services to help people quit smoking, targeting those at greatest risk from the dangers of tobacco.