Dangerously overweight children will have to be taken from their parents and put into care because of Britain's worsening "obesity epidemic", council leaders have warned.

One million children will be clinically obese within four years on current trends, storing up future problems from heart disease, strokes, high blood pressure and diabetes.

The Local Government Association (LGA), which represents 400 councils in England and Wales, predicted social services teams would have to take drastic action to improve the health of seriously overweight children.

Social workers have only become involved very rarely in such cases, considering the issue is best tackled by parents.

But the LGA warned that social services might have to treat very fat children as victims of "parental neglect" – just as malnourished children are.

It predicted that social services would have to intervene "more and more" with obese children. It added that councils would have to take action against parents who put their children's health at risk, with the ultimate sanction of taking the fattest boys and girls into care.

The LGA said Britain was fast becoming the "obesity capital of the world" and the increasing weight of the average citizen was pushing up council tax bills.

The costs come from the need for bigger furniture in classrooms, canteens and gymnasiums to cope with larger pupils. Crematoria furnaces are being widened at a cost of tens of thousands of pounds for heavier corpses. Ambulances are being re-equipped with extra-wide and strengthened stretchers and winches. Fire services are called in to winch obese people out of dangerous buildings. Local authority homes are being adapted for the overweight.

Social services costs are rising due to caring for house-bound people suffering from conditions caused by obesity such as arthritis, heart disease and diabetes.

David Rogers, the LGA spokesman on public health, said: "Councils are increasingly having to consider taking action where parents are putting children's health in real danger. Councils would step in to deal with an undernourished or neglected child, so should a case with a morbidly obese child be different? If parents place children at risk through bad diet and lack of exercise is it right for a council to keep the child's health under review?

"It is vital that councils, primary care trusts and the NHS work with parents to ensure children don't end up dangerously overweight in the first place. There needs to be a national debate about the extent to which it is acceptable for local authorities to take action in cases where the children's welfare is in jeopardy."

The Government faced criticism this month after it announced plans to warn parents if their child had a weight problem, but banned the use of the word "obese". The Department of Health is instructing primary care trusts to inform all parents automatically about their child's height and weight as part of a national measuring programme.

But ministers do not want the word "obese" to be used in the letters after research showed people find it "highly offensive".

A public health expert, David Hunter, of Durham University, this week warned that rising obesity levels posed as a grave a threat to Britain as terrorism and urged "bold action" by ministers.

A weighty issue

21 per cent

Proportion of boys aged six to 10 who will be obese in 2025. In 2004 the figure was just 10 per cent

14 per cent

Proportion of girls in the same age group who will be obese in 2025. In 2004 this figure was also just 10 per cent