Young women with larger than average breasts may have a higher risk of developing diabetes, a new study shows.

Researchers who studied over 90,000 women found those with above-average bra sizes at the age of 20 were up to 80 per cent more likely to get the disease than those with smaller breasts.

The scientists from the University of Toronto in Canada said the risks remained high, even when they allowed for whether the women were overweight, or had a family history of diabetes. This suggests breast size could be a new marker for who is most likely to develop the condition.

Around two million people in Britain are known to have diabetes but experts fear another one million are affected without realising it.

Most suffer from type two diabetes, which is often linked with fatty diets and lack of exercise. The pancreas stops producing enough insulin to help muscles mop up glucose circulating in the blood.

Left untreated, the disease can cause irreversible damage to the kidneys, eyes, nerves, heart and major arteries.

Doctors fear an epidemic of type two diabetes in the UK because of unhealthy lifestyles and are already seeing the condition being diagnosed at much younger ages.

The latest study, published in the Canadian Medical Association Journal, suggests screening young women for breast size could help.