Experts warn that one in ten people could be diabetic by 2030.
The charity Diabetes UK says rising levels of obesity mean 5.5 million adults will be infected within a decade.
And another 17 million will be at risk for type 2 because of their weight.
CEO Chris Esco said: “We are at the forefront of the public health emergency and action is needed today to stop it.
“It’s a serious thought that, if we don’t act, hundreds of thousands will face the life-changing news that they have type 2 diabetes.
“With proper care and support, complications of diabetes can be prevented and cases of type 2 diabetes can be forgiven or prevented altogether.”
Most people with type 2 diabetes – about 90% of all cases – get it because of an unhealthy lifestyle. Type 1 cannot be prevented.
Diabetes UK has called for government investment in weight loss programs, diabetes prevention and check-ups so that patients do not have complications.
Two-thirds of Britons are overweight. The NHS is already providing the world’s largest type 2 diabetes prevention program.