In a letter to England CMO Dame Sally Davies, the RCGP and 11 other organisations called on the government to establish a Child Obesity Action Group (COAG) of health professionals to support children's health.
Senior GPs at the college warned that a generation of children faced dying before their parents because of poor diet and lack of exercise.
They argued that GPs and other health professionals should be given additional training in malnutrition and obesity as part of the drive.
The letter also called for:
Increased support for the National Child Measurement Programme
Improved investment in data-gathering IT programmes for weight management
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.'
Fighting for children's health
She said child obesity treatment provision was a postcode lottery in much of the country, adding: 'We cannot allow our young people to become malnourished, squandering their childhood and vitality hunched over computer consoles and gorging on junk food.
'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 COAG will allow us to call up a "battalion" of health professionals to lead the fight for our children’s health.'
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.
'GPs and other healthcare professionals are now seeing a range of health problems in children that, in many cases, will develop into serious lifelong illnesses.'
'This crisis is happening'
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 2 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.'
Speaking to GP in April, Dr Pryke said the battle against obesity was 'a disaster that is happening around us'.
A DH spokeswoman 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.
'The CMO will formally respond to the letter addressing all the points raised in due course.'