A motion to be put forward at the British Medical Association's annual conference later this month will also say that childhood obesity should be treated by social workers as neglect in cases where parents refuse to listen to the advice of healthcare experts.

The recommendation comes amid growing concerns about Britain's obesity epidemic and the long-term health impacts for children as well as adults.

British children are among the most overweight in the world. In the UK, there are around one million obese children under 16 years of age and the prediction is that as many as one-fifth of boys and one-third of all girls will be obese by 2020.

The greatest rise has been among eight- to 10-year-olds.

These soaring rates have lead to an increase in childhood diabetes and experts warn that overweight children are putting themselves at risk of future heart disease, osteoarthritis and some cancers.

Measures introduced to tackle obesity include guidance from the government's health watchdog, the National Institute for Clinical Excellence , for morbidly obese teenagers as young as 14 to undergo weight loss surgery and for under 12s to be offered anti-obesity drugs in extreme cases. They also include a ban on all adverts for junk food during children's programmes and programmes watched by high numbers of under 16s.