The number of adult diabetics in the UK has soared by 6% since last year while obesity shot up by a similar amount, new figures showed today.
The data indicate one in 20 people is being treated for diabetes and almost one in 10 for obesity.
The increase in both conditions was described as "shocking" by a leading health charity.
Diabetes UK called on the Government to put into practice its rhetoric on tackling health problems through prevention.
Type 2 diabetes - which the vast majority of sufferers have - is strongly linked to being overweight or obese, leading a sedentary lifestyle and eating an unhealthy diet, the charity said. About 90% of diabetics (2.5 million people) have the Type 2 variety of the condition.
The figures, collected from GP practices, showed that some 2.8 million people aged 17 and over in the UK have diabetes - an increase of more than 150,000 since last year.
The nationwide figure of people over 16 registered as obese meanwhile has risen to more than 5.5 million - an increase of more than 265,000.
Simon O'Neill, Diabetes UK director of care, information and advocacy, said: "Once again we see a shocking rise in diabetes and obesity rates in the UK.
"Many, but not all, people develop Type 2 diabetes because they are overweight or obese so we must keep up the mantra of five fruit and veg a day, encourage daily physical activity and warn of the potentially devastating consequences of an unhealthy lifestyle.
"The obesity-fuelled Type 2 diabetes epidemic is a clear example of where the new coalition Government's rhetoric of tackling health problems through prevention must be turned into action.
"Failure to act now means a bleak future of spiralling NHS costs and worsening public health.
"Diabetes is serious. If not diagnosed early or poorly managed, it can result in blindness and amputation or a shortened life expectancy from heart disease, stroke and kidney failure."
Another health charity, the Child Growth Foundation, warned that levels of diabetes and obesity were likely to rise still further.
Honorary chairman Tam Fry said: "These figures confirm how appalling the levels of diabetes and obesity are in this country, and they would be even worse if they included children.
"Unfortunately we can expect levels to go up even if in some parts of the country obesity may be being brought under control. The fat are just getting fatter and suffering the consequences of excess weight."
The main risk factors for developing Type 2 diabetes are being overweight or having a large waist; being aged over 40 (or over 25 for black and south Asian people); and having a close relative with diabetes.
Symptoms of the condition include urinating very frequently, especially at night, increased thirst, extreme tiredness, unexplained weight loss, slow healing of cuts and wounds and blurred vision.
But in Type 2 diabetes the signs and symptoms may not be obvious and the condition can go undetected for up to 10 years, meaning about half of people already show signs of complications by the time they are diagnosed.
The Government will publish a white paper on public health before the end of the year, setting out plans to tackle obesity and help people lead healthier lives.
A Department of Health spokeswoman said: "The Government is committed to tackling obesity to help prevent more serious illness and much bigger costs to the health service and the country in years to come.
"We know that being obese and overweight increases the risk of a range of diseases that can have a significant health impact on individuals, including heart disease, Type 2 diabetes and certain cancers.
"What the Government can do is give people clear, consistent advice on why they should change their lifestyle, how to do so and put in place ways to make it easier."