Health experts have warned that the increase in the habit will lead to more heart attacks.

Preliminary results of the decade-long study conducted in 38 countries show smoking has increased in women aged between 35 and 64.

In many parts of the world, particularly Asia and Russia, the number of women who smoke has risen by as much as 10-20%.

'No obvious answer'

Vienna cardiologist Dr Kurt Huber said nobody had the answer as to why more women are smoking.

Dr Huber said improving living standards in less developed countries had lead more people to take up smoking.

In those countries, more educational programmes were needed to explain the dangers of smoking and provide advice on how to kick the habit.