The health of an entire generation of children could be "destroyed" by a diet of junk food and lack of exercise, doctors have warned.
As a result, GPs have called for an emergency taskforce to tackle childhood obesity and reduce the risk of future health problems.
In an open letter to the Chief Medical Officer for England, Professor Dame Sally Davies, the Royal College of General Practitioners (RCGP) and 11 partner organisations said a national Child Obesity Action Group (COAG) should be formed as "a matter of urgency".
The taskforce would be similar to the Government's Cobra panel, which deals with terrorism and national disasters, and would tackle "the rising epidemic of childhood obesity", a RCGP spokesman said.
Doctors, nurses, midwives, dieticians, dentists and schools would collaborate to try to prevent obesity and improve treatment services to stop children developing health problems in later life.
In the letter to the Chief Medical Officer, health leaders have called for a raft of other measures including:
:: Increased support for the National Child Measurement Programme
:: Improved investment in data-gathering IT programmes for weight management
:: More training in malnutrition and obesity for GPs and other health professionals
:: Outreach projects to educate families about the dangers of obesity
Dr Rachel Pryke, RCGP clinical lead for nutrition said: "The nutritional patterns laid out in early years can define a child's health for life and the stark fact is that overweight children are being set up for a lifetime of sickness and health problems.
"We are in danger of destroying the health of a whole generation of children. As parents and health professionals, we need to take responsibility and ensure that every child has a healthy and varied diet and regular exercise."
Dr Pryke said child obesity treatment was "a postcode lottery", with many areas having limited or no services at all.
"We cannot allow our young people to become malnourished, squandering their childhood and vitality hunched over computer consoles and gorging on junk food," she added.
"We have reached a state of emergency with childhood obesity and the current threat to public health is most definitely 'severe'.
"We need the right infrastructure, investment and knowledge to bring about the huge changes that are necessary if we are to protect the next generation.
"A national Child Obesity Action Group will allow us to call up a 'battalion' of health professionals to lead the fight for our children's health."
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Dr Richard Roope, RCGP clinical lead for cancer, said: "For the first time, we have a generation of patients who may predecease their parents. Only 3% of the public associate weight with cancer, yet, 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 where there was a notable fall in the number of smokers once prices were increased.
He added: "GPs aren't killjoys - we want all our patients to have healthy and fulfilling lives, whatever age they are- but this crisis is happening and it's real.
"We have a huge problem on our hands when seven-year-olds present in our surgeries with type two diabetes - something that was previously only ever associated with the weight gain of middle-age.
"We are in denial. Our children are currently amongst the most overweight in Europe. This statistic is something that we should all be extremely ashamed of and we all have a responsibility to take action and reverse the trend."
A Department of Health spokeswoman said the Chief Medical Officer would formally respond "in due course".
She said: "Tackling obesity is one of our major priorities, but there is no magic bullet to solve the problem, and everyone has a role to play. We know that childhood obesity is at its lowest since 1998 but more should be done. The Government is not considering a sugar tax."