Diabetes UK reported that 6,836 children and young adults have type 2 diabetes in England and Wales, according to data from GP surgeries.
Type 2 diabetes is more aggressive in young people as complications of the disease – which can include blindness, amputations, heart disease and kidney failure – can appear earlier.
Although the main driver behind the high figures is thought to be obesity, other factors which could also play a part include a family history and ethnic background, the charity added.
Diabetes UK warned that thousands more children and young people could be diagnosed with the condition over the coming years, as the latest figures on childhood obesity show that more than a third of children in England will be overweight or obese by the time they leave primary school.
It has called for better specialist support for youngsters with the condition to help manage their illness and reduce their risk of serious complications.
Meanwhile, the charity also backed proposals for a ban on junk food TV advertising aimed at children before 9pm, and to restrict supermarket price promotions for unhealthy foods.
“To help shape a future where fewer children develop the condition, we need continued commitment across society to create an environment that reduces obesity,” said Bridget Turner, director of policy and campaigns at Diabetes UK.
Turner said we need to encourage healthy living by providing easy-to-understand nutritional information about products people are buying, and protect children from adverts for foods that are high in fat, salt and sugar. She added that people who already have the condition need better support so they do not develop severe complications.
Professor Russell Viner, president of the Royal College of Paediatrics and Child Health, added: “For many children, the development of type 2 diabetes can be prevented with lifestyle changes, but this isn’t easy – they need support.”
In response to the figures, a Department of Health and Social Care spokeswoman said: “We are committed to halving child obesity by 2030 and will be launching consultations to restrict promotions in shops for sugary and fatty foods, as well as a 9pm watershed ban on advertising. The upcoming NHS long-term plan will have prevention at its core and build on our existing work to keep people healthy and well.”