The risk is linked to women who begin using HRT after suffering a heart attack.

A US study by the Duke Clinical Research Institute found that they were more than twice as likely to be admitted to hospital with chest pains within a year of having a heart attack as those who did not use the therapy.

Women who had been using HRT before they suffered their first heart attack ran a similar risk of hospital admission as those who did not take it at all.

Beneficial effect

The study is the second in a year to suggest a link between HRT and heart disease.

The University of California at San Francisco said last August that the risk of heart attacks seemed to increase soon after the therapy was started.

Previously, it had been thought that hormones had a beneficial effect on the heart.

Dr Karen Alexander, of the Duke Clinical Research Institute, said the studies showed the need to review advice on prescribing HRT for women with heart disease.

"While hormone use has benefits and may still be cardioprotective in women without heart disease, women who have heart disease should probably not start using them."

But she added: "We have no reason to suggest women stop using hormones if they develop heart disease."

Alexander and her team reviewed data on a 1996 study on the use of aspirin by heart attack patients. The study included 1,857 postmenopausal women.

The researchers found that more than 37% of women who started using HRT after their attack were admitted to hospital with unstable angina within around a year.

This compared with 17% for women who had never used hormones and 21% for those who had started HRT before they suffered their heart attack.

Dr Alexander said: "I hope there are other studies we can look back on that will help us further our understanding of who best benefits from hormone therapy."