A leading health expert has warned that tens of thousands of overweight children are in danger of dying before their parents.

Dr Colin Waine of the National Obesity Forum said obese children were up to 20 per cent more likely to develop cancer as adults than those of a healthy weight. He accused the Government of failing to defuse a health timebomb, and claimed GPs had been told not to prescribe weight loss drugs to save money.

Waine told BBC Radio 5 Live: 'An obese boy is 14 per cent more likely to develop cancer as an adult and an obese girl 20 per cent. '

He claimed Ministers were not taking the health risks seriously enough. 'In terms of childhood obesity there are so many cardiovascular risk factors present in children with serious obesity that we are in danger of breeding a generation who will die before their parents,' he said.

A health department spokesman said the Government was committed to tackling rising levels of obesity. He said prescriptions for obesity drugs had trebled and stressed the importance of local schemes encouraging children to take physical exercise.

The Government is awaiting a report this summer on a possible link between advertising and children's consumption of junk food. Chief Medical Officer Sir Liam Donaldson is shortly to unveil his report making recommendations on what can be done to promote healthy activity.