Hundreds of thousands of people on high-dose statins are increasing their chances of developing diabetes, researchers warn today.

Taking 80mg of two types of widely prescribed statin - simvastatin or atorvastatin - increases the chance of developing Type 2 diabetes by 12 per cent over five years, compared to taking moderate dose statins (20mg or 40mg), they found.

However, experts said patients should still take the cholesterol-lowering drugs as the benefits in terms of reducing the risk of heart attacks and strokes outweighed the risks.

In England about 200,000 people, mainly those who have already suffered a heart attack or stroke, take 80mg daily doses of simvastatin or atorvastatin.

Today's study, published in the Journal of the American Medical Association (JAMA), looked at almost 33,000 people on moderate or high-dose statins in five separate studies. None had diabetes to start with.

The researchers calculated that for every 498 people who took high-dose statins for a year, an extra person would develop diabetes than if they had taken moderate-dose statins.

However, if the same group took high-dose statins it would prevent at least three more cardiovascular events, compared to them taking moderate doses.

The academics, led by Dr David Preiss of Glasgow University, concluded: "Net cardiovascular benefit in high-risk individuals will still strongly favour statin therapy."

Their research complements a study, also involving Dr Preiss, published in The Lancet last year. It found that taking moderate doses of statins increased the risk of developing Type 2 diabetes by nine per cent over four years, compared with taking a sugar pill.

The researchers remain unclear about how statins appear to trigger diabetes in some individuals.

Professor Peter Weissberg, Medical Director at the British Heart Foundation, said: "Nobody should stop taking their prescribed statins because of the evidence shown in this research."

Dr Sharlin Ahmed, research liaison officer at The Stroke Association, said: "Every patient needs to be assessed and treated on a case by case basis and the risk of developing diabetes as a result of taking statins should be weighed up against the potential risk of having a heart attack or stroke."

Libby Dowling, clinical advisor at Diabetes UK, said: ”What we don’t know from this research is whether the people being prescribed the high-dose statins were overweight as having a large waist puts you at increased risk of developing Type 2 diabetes anyway.

“The benefits of statins for people at increased risk of heart disease outweigh the risk of developing Type 2 diabetes so we would not recommend people stop taking them on the basis of this research.”