There are far more children in the UK suffering from diabetes brought on by obesity than has previously been estimated, researchers warned today.

A study carried out in east London found 22 children under 16 with type 2 diabetes, which usually occurs in overweight people aged over 45, with some suffers just nine when diagnosed.

There could be as many as 1,500 under-16s with type 2 diabetes across the country, according to the researchers at Barts and the London and Newham University hospital NHS trusts.

The experts said their findings suggest a study two years ago that concluded only around 100 under 16s in the UK suffer from type 2 diabetes grossly underestimated the scale of the problem.

The new study, unveiled at the charity Diabetes UK's annual conference in Glasgow, found that 95% of the children with type 2 diabetes were either overweight or obese.

All but one of the children came from black and ethnic minority groups, among whom type 2 diabetes tends to develop sooner. Prevalence is also at least five times higher than other groups.

Ten years ago type 2 diabetes was unheard of among children, but it has begun to emerge as the obesity epidemic has exploded. Among youngsters aged two to four obesity almost doubled between 1989 and 1998 - from 5% to 9%. And in those aged six to 15, rates trebled from 5% in 1990 to 16% in 2001.

Jeremy Allgrove, consultant in paediatric diabetes at the East London Centre for Paediatric and Adolescent Diabetes, said: "Ten years ago we did not see type 2 diabetes in children under 16 but it is now increasingly becoming a part of paediatric practice."

Dr Allgrove added: "In addition to these children with diabetes, there is another group that have insulin resistance and are obese who are at risk of developing diabetes in the foreseeable future. This is a time bomb waiting to explode."

Douglas Smallwood, the chief executive of Diabetes UK, said: "These cases in east London confirm a shocking trend that type 2 diabetes in children is increasing.

"Diabetes can lead to long-term complications such as heart disease, blindness, kidney failure and reduced life expectancy. Unless children are educated to eat a healthy diet and take up physical activity, the number of children with the condition will continue to increase."

Mr Smallwood added: "Specialist diabetes services for children are already under a lot of pressure. If this problem is getting worse, the NHS has to ensure resources are in place to deal with it."

Type 1 diabetes, which is not linked to obesity, accounts for the majority of cases of childhood diabetes.