The bid to halt rising child obesity by 2010 will fail unless the government shows more leadership, a study says.
Obesity costs the NHS £1bn a year
Public sector watchdogs the National Audit Office, Healthcare Commission and Audit Commission said there was good work going on at a local level.
But they said government departments needed to offer more guidance as there was confusion about the push.
Public Health Minister Caroline Flint said "huge steps" had been made, but added more had still to be done.
The number of obese children has increased from 9.6% in 1995 to 13.7% in 2003.
The overall cost of obesity to the NHS is currently around £1bn, with a further £2.3bn to £2.6bn for the economy as a whole.
Rates - Over 13% of under 11s in England are obese, up from 9.6% in 1995
International comparison - The UK has one of the highest obesity rates in Europe - more than three times the level of France. But it still lags behind the US, Mexico and Argentina
Cost - The bill for the NHS is £1bn a year and for the wider economy it totals over £2bn and is rising
The target was set in July 2004 in a bid to unite the various partnerships between councils, the NHS, voluntary sector and schools into tackling childhood obesity.
But despite being 18 months into the campaign key parts of the delivery plan have still not being published.
And guidance to primary care trusts on measuring children was only published in January.
This means youngsters will not start to be measured until the summer and initial results probably not available until next year - just three years before the target is supposed to be met.
The target is the joint responsibility of the Department of Health, Department for Education and Skills and the Department for Culture, Media and Sport, and states that rising rates of obesity in those under the age of 11 must halt by 2010.
The report warned that a "lack of timely guidance" had meant that organisations supposed to be working together to stop rising childhood obesity had been unclear about their roles.
Schools, in particular, needed better guidance to increase the use and accessibility of sports facilities.
Steve Bundred, chief executive of the Audit Commission, said the target to halt rising obesity in under-11s was "very complex and ambitious".
"The causes of obesity are very varied.
"Tackling it requires tackling a whole range of lifestyle and behavioural issues."
Anna Walker, chief executive of the Healthcare Commission, said childhood obesity was a major issue for the nation's health and the provision of healthcare.
"Children who are overweight tend to grow into adults who have a range of health problems as well."
Paul Sacher, founder of the Institute of Child Health's Mend Programme, which works with families on adopting healthier lifestyles, accused the government of lacking ambition.
"We should be trying to reverse the trend, not just halt it. We have shown that if you address diet, exercise and behaviour you can make a difference.
"But to date we have had little lead by the government, it has been too slow."
Ms Flint said "huge steps" have already been made.
"Our public health agenda is the first concerted attempt to seriously tackle rising levels of obesity."
But she added: "We know that leadership and co-ordination are going to be crucial as is giving people information and support in making a difference to their own lives. We recognise we need to do more."