The government has quietly abandoned its target to halt childhood obesity by 2010, setting instead the goal of reducing it by 2020 - a decade further on.

The move comes in the response today of the public health minister, Dawn Primarolo, to the Foresight report, a two-year trawl through the evidence by scientists which concluded that the problem was huge, could cost the UK £45bn a year and could take 30 years to turn round.

While it was acknowledged the government target was ambitious when it was set in 2004, many critics say that to take the pressure off by allowing the childhood obesity goal to slip by 10 years is unwise.

There was also disappointment that neither the much-anticipated Foresight report nor the government response contained any kind of blueprint for action.

The British Heart Foundation said the report was not so much a wake-up call as an echo of alarm bells that have been ringing for more than 30 years. "Repeated reports like this, which should have had alarm bells ringing in Whitehall long ago, have been met only by repeated pushes of the government's snooze button," said Peter Hollins, the foundation's chief executive. "Combating childhood obesity was part of New Labour's election manifesto in 1997."

The foundation expressed its concern at the softening of the target on childhood obesity. Mr Hollins said: "Setting new targets for 2020 is presumably a tactic to buy the government more time to get its act together, but it risks making the problem seem too distant to force through the necessary bold measures in this term.

"The prime minister needs to be braver than his predecessor and show the country he has the bottle to rein in the pervasive influence of the food industry over our children's eating habits."

Ms Primarolo said in response to the Foresight report that tackling childhood obesity was a key cross-government priority. Progress had been made, she said, citing healthier school food, clearer food labelling and tougher advertising restrictions on junk food, "but we know that we need to go further and faster", she said.

The initial focus of the anti-obesity drive would be children, she said. "By 2020, we aim to reduce the proportion of overweight and obese children to 2000 levels."

The Department of Health said later: "When we set the original 2004 target we knew this would be a challenge. Obesity levels are growing throughout the developed and developing world, and there is very limited evidence of international success at halting or reversing this trend.

"We have reconsidered the position in the light of emerging evidence." It added that the altered target was signalled in last week's comprehensive spending review.

The central message of the Foresight report, put together by a team headed by Sir David King, the government's chief scientific adviser, was that there was no simple answer to the problem. The nation had "sleepwalked" into it because our hunter-gatherer biology was out of step with the technological convenience age; we were programmed to eat as if we did not know where the next meal was coming from. "If we just behave normally we will become obese," Sir David said.

It is neither entirely the fault of the individual nor of society, Foresight says. There is no magic bullet solution, and no wonder diet drug will do the trick. Foresight draws many parallels with climate change, saying that changes in many different areas of society are necessary, from the design of towns and transport systems to encouraging healthier food production and consumption.

If current obesity levels continue, about 60% of men, 50% of women and 25% of children in the UK will be obese by 2050.

The Children's Food Campaign, an alliance of more than 300 organisations, said the report showed the obesity timebomb was exploding. "We need urgent action to help people, especially children, avoid the less healthy, less happy and, ultimately, shorter life that obesity leads to," said its coordinator, Richard Watts. "The government should end junk food TV advertising before 9pm, as the first step in a longer campaign to change our food culture."

The consumer organisation Which? urged the government to go "further and faster" by bringing in tougher rules, within three months, against the promotion of unhealthy food to children. "Obesity is a complex problem but the solutions currently on the table are not up to the task," said its chief policy adviser, Sue Davies.

· Food blog: Rebecca Smithers on the obesity crisis