LONDON - More than 22,000 kids in England and Wales aged 10 and 11 are severely obese when they leave primary school, a report by the Local Government Association (LGA) warned Tuesday.

The number classed as the most overweight on the obesity scale is nearly double the total of four and five year old children who were obese when they first started school.

The LGA, which represents 370 town and city councils in England and Wales, warned that severe child obesity rates, which have been published for the first time, are contributing to a multi-billion dollar ill-health time bomb.

The first data of its kind obtained by the LGA and supplied by the National Child Measurement Program (NCMP), revealed that a total of 22,646, or 4.1 percent, out of more than half a million 10 and 11-year-old children in their final year of primary school are officially classed as severely obese ahead of their transfer to senior schools.

The LGA said: "Severe obesity rates vary significantly by area and are highest in children living in the most-deprived towns and cities, and those from BME groups, suggesting a need for the development and evaluation of more targeted interventions."

The figures, added the LGA, should serve as a wake-up call for concerted action to tackle the obesity crisis which is costing the NHS more than $6.6 billion a year.

"Despite budget reductions, councils are spending more on running effective prevention schemes to help children stay healthy, which is key to tackling the child obesity crisis and reducing future costs to hospital, health and social care services," said the report.

But the LGA warned essential prevention work, including the ability of councils to provide weight management services for children, is being hampered by an $800 million reduction in councils' public health budgets by Britain's central government.

The LGA called for reductions in public health grants to be reversed by the government and for further reforms to tackle childhood obesity. This includes councils having a say in how and where the soft drinks levy is spent, better labelling on food and drink products, and for councils to be given powers to ban junk food advertising near schools.

Izzi Seccombe, chair of the LGA's Community Wellbeing Board, said: "These new figures on severely obese children, who are in the most critical overweight category, are a further worrying wake-up call for urgent joined-up action.

"The UK is already the most obese nation in western Europe, with one in three 10 and 11-year-olds and one in five four and five-year-olds classed as overweight or obese, respectively.

"Unless we tackle this obesity crisis, today's obese children will become tomorrow's obese adults whose years of healthy life will be shortened by a whole host of health problems including diabetes, cancer and heart disease."