The number of people with diabetes in the UK is now more than 3.2 million, with last year seeing the biggest jump in cases since 2008.
NHS figures show 3,208,014 adults are now diagnosed with the condition. Around 850,000 more people have diabetes without knowing it.
The rise is being fuelled by cases of type 2 diabetes, which is linked to obesity and unhealthy lifestyles.
Last year, there were 163,000 more people across the UK who have been diagnosed with diabetes compared to 2012.
This is the biggest yearly increase since 2008, when the jump was 167,000. It means 6% of UK adults are now diagnosed with diabetes.
In 1996, the number of people diagnosed with both types of diabetes was thought to stand at about 1.4 million.
While the overall rise could be partly down to improvements in recording and diagnosis, experts at Diabetes UK, which analysed the figures, said the sharp rise over the last decade - fuelled by type 2 - shows no signs of slowing down.
The charity warned that more needs to be done to target those at risk of type 2 as well as improving healthcare for all people with diabetes.
The figures come after Cardiff University researchers said last week that insulin use has trebled over the last 20 years in the UK, driven by high rates of type 2.
Type 1 diabetes, which accounts for around 10% of all cases, usually develops in childhood.
Baroness Young, chief executive of Diabetes UK, said: "The big increase in the number of people with diabetes confirms that we are in the middle of an unfolding public health disaster that demands urgent action.
"It is frightening to think that one in 17 people you walk past in the street has been diagnosed with the condition.
"Firstly, we need more focus on preventing type 2 diabetes, as this is the only way we can bring the rapid rise in diabetes cases under control.
"This means properly implementing the NHS Health Check so we can identify more people at high risk and then making sure they get the support they need to reduce that risk.
"We also need to address the obesity crisis, which is what is fuelling the increase in type 2, by making healthy food cheaper and more accessible and by making it easier for people to build physical activity into their daily lives."
Lady Young called for action to treat diabetes "b ecause the level of priority the NHS gives the condition does not reflect the size of the shadow it is casting over our nation's health".
She said diabetes accounts for 10p of every pound the NHS spends but healthcare is patchy and inconsistent.
Around 80% of NHS spending on diabetes goes on treating complications of the condition, such as amputation, kidney failure, heart disease and stroke.
She said: "While some areas do provide excellent care, this is not happening often enough.
"From access to education when people are diagnosed, right the way through to the care they receive in hospital, there are too many people getting a raw deal and this is fuelling high rates of diabetes related complications and early death.
"The complications of diabetes are not only devastating for the people involved, but they are also very expensive to treat. With the number of people with diabetes continuing to rise, there is now an urgent need to grasp the nettle and start focusing on the ongoing care and support for self-management that can help prevent complications happening in the first place.
"Unless we do this, we are likely to see more people having to endure complications and an accompanying rise in diabetes spending that we will simply not be able to afford."
Professor Jonathan Valabhji, national clinical director for obesity and diabetes at NHS England, said: "It is widely known that we are seeing huge increases in type 2 diabetes - driven largely by rising rates of obesity.
"Prevention has to be a crucial part of our approach and the risk of developing type 2 diabetes is significantly reduced with a healthy lifestyle.
"NHS England is putting a real emphasis on prevention alongside screening for high risk or the presence of type 2 diabetes through NHS health checks.
"Better education and management of diabetes including good access to specialist care is also the best way to prevent complications."
Diabetes UK says as many as seven million more people are at high risk of developing type 2 diabetes and, if current trends continue, an estimated five million people will have diabetes by 2025.