The government has failed to tackle obesity - and unless it does so, the future of the NHS hangs in the balance, says the man who persuaded ministers to pump record sums into the service.

The government has failed to tackle obesity - and unless it does so, the future of the NHS hangs in the balance, says the man who persuaded ministers to pump record sums into the service.

Sir Derek Wanless has been hired by the King's Fund to examine the impact of the billions ploughed into the NHS since his groundbreaking 2002 report.

The study will assess whether the extra billions have been spent wisely and, if not, how services and funding need to change. He will look at progress against the ideal 'fully-engaged scenario' he set out, under which people would take more responsibility for their own health.

Speaking exclusively to HSJ, he warned that failure to improve the nation's health would create pressure to consider alternatives to a state-funded NHS.

The original 2002 report by the former NatWest banker warned that unless much more money is spent on health promotion, the NHS would face its worst-case scenario of 'slow uptake', leaving taxpayers to fund greatly increased numbers of people with diabetes and heart disease in 20 years' time.

This week he warned that obesity is still on the rise - a situation even worse than 'slow uptake', whereby levels remained unchanged.

Sir Derek's 2002 report outlined two more positive scenarios: 'steady progress', which would have meant bringing prevalence of obesity down to 6 per cent for men and 8 per cent for women by 2022, and 'fully engaged', which exceeded these goals.

The Department of Health's most recent health survey in August warned that on current trends, by 2010, 33 per cent of men will be obese, and 28 per cent of women.

This week Sir Derek said: 'Obesity is slow uptake without any doubt. It's not even stabilising.'

'We'll be looking [in the report] at what implications this will have for the future of the health service, and how our assumptions on future funding levels will need to change.'

He said that unless more effective moves are made by ministers to deal with obesity, the necessary funding might overwhelm the NHS and could even make it easier for politicians to argue for an end to a fully-funded tax-based health service.

'If people begin to believe it's a terribly inefficient service, they may begin to question what they are prepared to pay for,' he warned.

'There will be pressure to improve delivery and that could lead to a reduction in services or a change in the method of funding. It could herald the social insurance revolution; who knows?'

He told HSJhe backed the Conservative Party's aim to make the Department of Health more focused on public health: 'I have been saying for a long time that I think the secretary of state should be secretary of state for public health,' he said. 'The whole health of the nation should be her [Patricia Hewitt's] priority.'

He also said he was interested in ideas floated by Conservative leader David Cameron and chancellor Gordon Brown for greater NHS independence - but that it depended what the phrase meant.

'It depends who makes decisions about funding; who sets the targets. These are issues that need to be sorted out. You can't just carve out an NHS organisation and say &Quot;do what you like&Quot;. Independence in practice will mean a very tightly defined framework.'

Sir Derek said he hoped his report would help take some of the political point-scoring out of the NHS by setting out clearly what has been achieved and what has not.

In the summer, Ms Hewitt notoriously said the NHS has had its 'best ever year'. Asked about the phrase, Sir Derek said: 'I am sure you can point at some places where things have gone very well but there are bound to be areas where things have not gone right,' he said.

'We are trying to look at the situation overall and trying to avoid that sort of sloganising that polarises political debate and often does not mean very much.'

In his 2002 report, Sir Derek called for a five-yearly review to be carried out by the Treasury. This week he said he was 'past being disappointed' that a think-tank was being left to fund the report in the absence of government action.

ButKing's fund chief economist Professor John Appleby said it was a shame the Treasury hadn't commissioned its own report. 'We hope it will provide a spur for the government to be more serious about this,' he said.