Childhood obesity in England has doubled in 10 years, figures show.
Obesity costs the NHS £1bn a year
One in four children is obese, the Health and Social Care Information Centre survey of 2,000 children found.
From 1995 to 2004, obesity among boys aged 11-15 rose from 14% to 24% and girls from 15% to 26%. The rate rose slightly in the two to 10 age group.
Campaigners said England was facing a "health timebomb", and ministers said more had to be done to hit the target to halt the child obesity rise by 2010.
Earlier this year, public sector watchdogs the National Audit Office, Healthcare Commission and Audit Commission said good work going on at a local level.
But they added the government needed to show more leadership if the push was to succeed.
Public Health Minister Caroline Flint said: "We recognise we need to do more.
"Our public health agenda is the first concerted attempt to seriously tackle rising levels of obesity."
She added "huge steps forward" have already been taken through campaigns to increase fruit and vegetable consumption and more investment in school sport.
The survey also showed adult obesity is continuing to rise from 13% to 24% for men and 16% to 24% for women.
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.
Professor Colin Waine, chairman of the National Obesity Forum, said the figures revealed a "public health timebomb".
"This is serious news because obesity in adolescence is associated with the premature onset of Type 2 diabetes and cardiovascular diseases.
"It really augurs very badly for the future health of the population as these children move from adolescence to adulthood.
"This will have a significant impact on longevity and we are in danger of raising a generation of people who have a shorter life expectancy than their parents.
"This is a public health timebomb as these children move into adult life."
And Weight Concern executive director Caroline Swain added: "If we are to preserve the health of the next generation, there is a desperate need for detailed research into what is triggering this rising trend, as well as practical action on a national level to encourage families to adopt healthier lifestyles."
Shadow Health Secretary Andrew Lansley said: "In the last decade British children have got fatter faster than anywhere else in Western Europe. We are at risk of an epidemic of vascular diseases as a result.
"The government's white paper in November 2004 talked about an obesity strategy but the implementation has been virtually non-existent."