Most of these -1.5 million - are suffering from type 2 diabetes, and a further million are likely to have the condition without being diagnosed yet, said the new report from Diabetes UK.
The number of people with the condition, now 3 per cent of the population, will continue to rise as the population ages and becomes more overweight, noted the charity.
Douglas Smallwood, chief executive of Diabetes UK, noted: "Many of the worst effects of diabetes can be avoided. We cannot afford to wait until people have heart attacks or have problems with their sight or kidneys before they get the care they need."
The report underlines the huge task that faces the UK government. It has already provided funding worth £2.7 million (€4m) through its Food Standards Agency for a four year study that will look at the impact of fat and carbohydrate on the chances of developing a collection of risk factors linked to heart disease and type 2 diabetes.
"Scientific studies on the optimum dietary strategy for reducing the risk of the metabolic syndrome are limited," said Dr Julie Lovegrove, lead researcher from the University of Reading, when the study was announced.
The global incidence of these risk factors, collectively known as the 'metabolic syndrome', is soaring. The clinical conditions linked to the metabolic syndrome are obesity, type 2 diabetes, abnormal blood fats and raised blood pressure. Each of these conditions is a risk-factor for the metabolic syndrome in its own right, but if individuals have more than one of these conditions the risk is multiplied.
Risk factors associated with metabolic syndrome - which affects up to 25 per cent of UK adults - include obesity, raised blood pressure and abnormal blood fat levels. In most cases, development of the metabolic syndrome is caused by eating too much of the wrong kind of foods and taking too little exercise.
Further research into the impact of diet on these risk factors could however help supplement and functional food makers offer products designed to reduce risk for some of the thousands forecast to develop the disease.
And while there is little evidence so far to support either the safety or efficacy of nutritional supplements in helping to improve diabetes-related conditions, there are some foods and nutrients, such as dark chocolate and magnesium, that warrant further investigation, Dr Michael Quon, chief of the diabetes unit of the US National Center for Complementary and Alternative Medicine (NCCAM) told NutraIngredients.com earlier this year.
Governments should see this type of research as an important strategy for reducing costs. Five per cent of the UK's National Health Service budget or around £10 million a day is currently spent on treating diabetes and its effects. NHS spending on the condition is predicted to rise to 10 per cent by 2011.