The number of young people being treated for Type 2 diabetes has risen by 40% in just four years to more than 700, figures show.
The condition, most commonly seen in adults, occurs when the body cannot produce enough insulin to regulate blood sugar levels and can be linked to obesity.
Council leaders described the increase as “extremely worrying” and called for a boost in local funding to help tackle the public health crisis.
The figures, from an audit published by the Royal College of Paediatrics and Child Health (RCPCH), reveal 715 people under the age of 25 received care for Type 2 diabetes from specialist paediatric units in England and Wales in 2016/17.
Of those children and young people, 78.6% were also obese.
This is an increase of 41% from 2013/14, when there were 507 cases.
The data only includes young people treated in paediatric units and not by their GP, and it is believed the true number of young people affected could be much higher.
Professor Russell Viner, president of the RCPCH, said: “A rise in Type 2 diabetes of this magnitude is alarming and shows that the childhood obesity epidemic is starting to bite.
“It’s also concerning that we might not be seeing the full picture.”
The Local Government Association (LGA), which represents 370 councils in England and Wales, urged the Government to boost investment and to provide specialist support for the most severely obese children.
Izzi Seccombe, chairwoman of the LGA’s community wellbeing board, said: “These figures are a sad indictment of how we have collectively failed as a society to tackle childhood obesity, one of the biggest health challenges we face.
“Type 2 diabetes typically develops in adults over the age of 40, so while still rare in children, it is extremely worrying that we are seeing more young people develop the condition.”
She added: “We need urgent action now. Type 2 diabetes can be a lifelong debilitating illness and these figures will only multiply if we delay.
“Councils with their public health responsibilities are on the frontline fighting obesity but for this to work effectively they need to be properly resourced.
“Cutting their public health funding is short-sighted and undermines any attempt to help our children live healthy and fulfilling lives.”
Almost half of those treated for Type 2 diabetes in paediatric units in 2016/17 were black or Asian, the figures also show, and the LGA said greater support is needed for ethnic minority groups.
Kathryn Kirchner, clinical advisor at Diabetes UK, said: “Although there are a number of risk factors for Type 2 diabetes which are out of our control, one of the most important risk factors is being overweight or obese, which we are able to influence.
“These figures are a stark reminder that we have a collective responsibility to push for the actions outlined in the most recent chapter of Childhood Obesity Plan, including clearer and more consistent food labelling.”
Type 2 diabetes can lead to a range of health problems such as heart disease, strokes and kidney problems.
Eustace de Sousa, from Public Health England, said: “The rise in type 2 diabetes in young children highlights why bold measures are needed to tackle childhood obesity – and change won’t happen overnight.
“That’s why we’re working with industry to make food healthier, we’ve produced guidance for councils on planning healthier towns and we’re delivering campaigns encouraging people to choose healthier food and lead healthier lives”.
A Department of Health and Social Care spokeswoman said: “We know the damage obesity causes and are determined to halve childhood obesity by 2030.
“We’ve invested billions in public health services and have already removed the equivalent of 45 million kilograms of sugar from soft drinks every year.
“Our new childhood obesity plan will now get children exercising more in schools and reduce their exposure to sugary and fatty foods.”