Fat parents could be paid to walk their children to school

Under the scheme people who exercise would receive supermarket-style vouchers to spend on sports gear and healthy food.

Those attending keep-fit classes or weight loss clubs could be eligible for rewards, as well as those walking to bus or train stations.

Critics claim the rewards will be a form of bribery. It is thought machines would be placed in schools or stations so parents or commuters could swipe their cards to tot up points.

The proposal will be assessed during a pilot project in Manchester, one of nine areas designated as "healthy towns".

It will be announced today by Alan Johnson, the Health Secretary, who will encourage every business to take action agains obesity.

But the plans have caused controversy, with small business leaders warning that they were already too stretched and that the current economic climate was "not the right time" to ask them to do more.

Mr Johnson is expected to say that a massive effort is required to alert the nation, and especially parents, to the risks of obesity, as he outlines plans for a nationwide £325 million "revolution" on the problem.

Research for the Department of Health shows that almost nine out of ten parents fail to recognise that their children are overweight or obese.

Experts predict that half of adults could have weight problems by 2050, creating a health crisis expected to cost the NHS £50 billions.

More than 12,000 businesses, charities and local groups have signed up to help promote the Government's campaign.

But Mr Johnson has called for more to join their number.

He said: "I am today challenging every CEO of every company who can influence what we eat and how we exercise to come forward and tell us how they are going to help beat this national epidemic.

"Obesity affects us all so everyone must get involved."

But Stephen Alambritis, from the Federation of Small Businesses, said that it was "not the right time" to ask more of small employers.

He said: "If this message is targeted to the CEOs of the top FTSE companies that is understandable but at the moment many small employers are struggling to keep their staff on the payroll and it is not the right time to ask more of them."

Businesses which have signed up to the initiative include ITV, which is to run a series of programmes tracking viewers' attempts to live healthier lives, and Kellogg's, the cereal giant, which will support breakfast clubs in deprived areas.

The Department of Health said that it had also come to "unprecedented" arrangements with Tesco and Asda, the supermarkets, to offer discounts on healthy food.

"Ten million people visit their corner shops every day and 36 million shop at Asda and Tesco each week - the fact that grocers and supermarkets are on board means we can really influence what goes into our shopping trolleys," Mr Johnson said.

"It's unprecedented for supermarkets to join the Government and pledge to cut prices on healthy food. But this isn't an exclusive club. Anyone who promises to help families to be healthier can join."

Mr Johnson said that research had shown that the challenge of convincing parents to change their habits would be difficult.

He said: "The message that we received from parents was clear: we recognise that obesity is a big problem, but it's not our problem."

"The aim of Change4Life is to help parents understand that obesity is a problem for all of us and that it causes severe illnesses and premature death.

"Finger wagging and lecturing won't work, that's why Change4Life is designed to be supportive and helpful."

Research commissioned for the Department of Health shows that just 11.5 per cent of parents whose children were overweight or obese children recognised that they had a problem.