This was revealed as part of a 15-year US study of 4,572 people which backed earlier claims that smokers were at higher risk of developing glucose intolerance - a precursor to diabetes. Another revelation was that people subject to second-hand smoke had a slightly higher risk of diabetes.
British Medical Journal has the study published and it suggests smoke toxins could affect the pancreas, which makes the blood sugar regulator insulin.
Professor Thomas Houston of the Birmingham Veterans Affairs Medical Centre in Alabama led the researchers and divided their subjects into smokers, former smokers, passive smokers and those never exposed to smoke. Thereafter, subjects were tracked down how many had developed glucose intolerance.
They found smokers faced the highest risk, with 22% getting the condition over the 15-year period. But 17% of those who never smoked themselves, but had been subject to second-hand smoke, went on to develop the condition.
The explanation is that passive smokers are exposed to toxins similar to those of active smokers, but some toxic substances are even more concentrated in passive smoke.
"We identified passive tobacco exposure in never smokers as a new risk factor for glucose intolerance. If confirmed by further research, these findings provide further documentation of the deleterious effects of tobacco smoking, and policy makers may use them as additional justification to reduce exposure to passive smoking."
Zoe Harrison, care adviser at Diabetes UK said, "If we needed another reason for banning smoking in public places, the risk of blindness, heart disease and amputation that can be caused by Type 2 diabetes should be pretty compelling. Diabetes is already increasing at an alarming rate and lifestyle factors definitely play a huge role in this. If this pattern continues, we will soon start seeing people losing their sight or having amputations at a much younger age.