Diabetes "threatens to bring down the NHS", Diabetes UK has warned.
Cases in England and Wales have risen by 59.8% in the past decade - as an additional 1.2 million adults are now living with the condition compared to ten years ago.
The figures, extracted from NHS data and analysed by the charity, show that 3,333,069 people have been diagnosed with the disease.
Diabetes UK warned that there is an urgent need for effective care for sufferers, while more must be done to highlight the importance of prevention.
The charity said that six in ten people in England and Wales receive the eight care processes recommended by the National Institute for Health and Care Excellence (Nice), and added that poorly managed diabetes can lead to "devastating and expensive health complications" including amputation and stroke.
"This is why it's critical that the Government takes urgent action to ensure that everyone with diabetes receives the eight care processes, reducing their risk of further health complications and the costs these incur for the already strained NHS budget," the charity said.
Barbara Young, chief executive of Diabetes UK, explained: "Over the past decade, the number of people living with diabetes in the UK has increased by over one million people, which is the equivalent of the population of a small country such as Cyprus. With a record number of people now living with diabetes in the UK, there is no time to waste - the Government must act now.
"We need to see more people with diabetes receiving the eight care processes recommended by Nice. It is unacceptable that a third of people living with the condition do not currently get these, putting them at increased risk of developing complications, such as amputations, heart attack or stroke."
She added: "Diabetes already costs the NHS nearly £10 billion a year, and 80% of this is spent on managing avoidable complications. So there is huge potential to save money and reduce pressure on NHS hospitals and services through providing better care to prevent people with diabetes from developing devastating and costly complications.
"The NHS must prioritise providing better care, along with improved and more flexible education options, for people with diabetes now, and give them the best possible chance of living long and healthy lives. Until then, avoidable human suffering will continue and the costs of treating diabetes will continue to spiral out of control and threaten to bankrupt the NHS. Now is the time for action."
The charity predicts that if current trends continue, five million people will have diabetes by 2025.