Doctors are calling for an emergency taskforce to stop obesity destroying children’s health.
GPs say the group should be like the Government’s Cobra panel, which deals with terrorism and national disasters.
They warn the NHS will be overwhelmed without action to cut the consumption of junk food, including a tax on sugary drinks.
Obesity now costs the health service £4.2billion a year.
Medics outline their fears about Britain’s youngsters – among Europe’s fattest – in a letter to Chief Medical Officer Professor Dame Sally Davies sent at the start of the new school term.
The Royal College of GPs and 11 other organisations call for a Child Obesity Action Group to be set up urgently.
It would bring together doctors, nurses, midwives, dieticians, dentists and schools to help children avoid the worst food and drinks.
The letter calls for more measuring of children’s weight, more training on the issue for GPs and health workers, and better education for parents about obesity risks.
Dr Rachel Pryke, the Royal College’s clinical lead for nutrition, said: “Overweight children are being set up for a lifetime of sickness.
“We are in danger of destroying the health of a whole generation.
"As parents and health professionals, we need to take responsibility and ensure every child has a healthy and varied diet and regular exercise.
“We cannot allow our young people to become malnourished, squandering their childhood and vitality hunched over computer consoles and gorging on junk food.
"We have reached a state of emergency with childhood obesity and the current threat to public health is most definitely severe.”
The doctors point out that obesity, now affecting 31 per cent of children, can lead to cancer and many other diseases, including diabetes.
Dr Richard Roope, the Royal College’s clinical lead for cancer, warned that today’s children could be the first generation to die before their parents.
He said: “For the first time we have a generation who may predecease their parents.
"After smoking, obesity is the biggest reversible factor in cancers.
“Radical steps need to be taken – at the very least levying tax on sugary drinks. We’ve seen this approach work with smoking.
“We have a huge problem when seven-year-olds present with type 2 diabetes, previously associated with the weight gain of middle age.
"Our children are among the most overweight in Europe.
"This is something we should all be ashamed of. We have a responsibility to reverse the trend.”