By Martin Hutchinson BBC News Online health staff

I do solemnly swear to cut down on...

The government, it is claimed, is considering asking heavy smokers or fat people to sign contracts promising to behave better in future before they receive certain treatments on the NHS.

Random blood tests for signs of a crafty smoke, or, for that matter, covert surveillance of cream bun-related activities is not yet, apparently, part of the plan.

In truth, nobody is suggesting turning away people with "self-inflicted" illnesses from the surgery door.

But if nothing else, it has raised the blood pressure of patient group campaigners up and down the country. And that can't be healthy, can it?

Patients' Association chief Claire Rayner told the BBC: "It's middle class garbage. I loathe it. It's repellent."

The Department of Health has issued soothing words about the true nature of its "joint statement of mutual good intent", plans for which could end up in the next Labour manifesto.

A possibility floated by the department was that a smoker might have to agree to go on a quitting smoking course before their free nicotine patches get handed over.

Rights and responsbilities

They point out that in return, doctors will be bound by the deal to offer a certain standard of service.

It's middle class garbage Claire Rayner, Patients' Association

Claire Rayner is also dismissive of this: "Doctors are bound to standards of care anyway. It's the job they do."

Health policy seems to work in a 10 year cycle, and keen observers will note that we have been here before.

The Patient's Charter, launched in 1991, focused mainly on what the patient could expect to receive from the health service, but included a section entitled "How you could help the NHS".

The measures could help the anti-smoking drive

Among the rather meek requests were pleas to return your NHS crutches to A&E, and not to get your GP out of bed in the middle of the night to deal with your ingrowing toenail.

"Remember that you benefit if your GP has a good night's sleep," it implored.

Healthy voters

The charter was widely derided - so why does Labour believe that there may be votes to be had in telling fat people to get on their exercise bikes?

It is possible the idea will appeal to a section of the public which resents the fact that a large slice of the NHS appears to be spent on so-called "lifestyle illness".

Smoking-related disease is thought to cost the NHS an estimated �1.5 billion a year, while obesity rates rivalling those in the US are leading to an epidemic of disabling type II diabetes.

I think doctors are going to be rather uncomfortable with this role Dr Stephen Wilkinson, Warwick University

But there is increasing evidence that the economic benefits of a smoke-free society are dubious to say the least.

If every smoker in the country gave up tomorrow, the government would lose almost eight billion pounds a year in tobacco duty.

In addition, studies have worked out that the new, long-lived former smokers would end up costing the state a similar amount when they died 15 years later of something else - in addition to the additional cost in pensions and benefits drawn in the meantime.

Dr Stephen Wilkinson, a lecturer in medical ethics from Keele University, said: "It could be argued that in terms of state finances, smokers may actually be a good thing."

Ethical tightrope

He argued that doctors who attempted to introduce contracts between themselves and a patient would walk a fine line between acceptable and unacceptable behaviour.

There were some instances in which witholding treatments from irresponsible patients might not constitute a breach of ethics, he said.

You never know where to draw the line - so it's best not to try to draw one John Appleby, Kings Fund

"There are some instances in which this happens already - for example, a surgeon who tells a patient that he will not operate unless he or she loses two stone because the operation will not work or may even be more dangerous."

However, he said that when it came to deciding who received scarce NHS resources, it might be perfectly proper to come down in favour of someone whose lifestyle would maximise the effectiveness of the treatment.

They'll never take me alive!

"There is an argument to be made that a contract might work if a change in lifestyle would make the treatment more effective."

He added: "However, it is a great deal more dubious if it is done in a punitive way - with the doctor saying: 'You've brought in on yourself, so I'm not treating you.'

"I think doctors are going to be rather uncomfortable with this role."

Unhealthy activities

John Appleby, a health economist with The Kings Fund, an independent think tank, agreed that there was nothing wrong with spending scarce NHS money on those most likely to benefit.

"We call it 'directing them to the people with the capacity to benefit' - which, I suppose, is this route in the end."

However, he said that witholding treatment on the basis of lifestyle was a non-starter.

"You could include smoking, but shouldn't you also put in skiing?

"Even getting out of bed in the morning is a health risk.

"You never know where to draw the line - so it's best not to try to draw one."

Time to change

However, Dr Richard Nicholson, the editor of the Bulletin of Medical Ethics, says that something needs to be done to change the attitudes of a hard-core of people who expect the NHS to bail them out regardless of their own behaviour.

He told BBC News Online: "There has been the belief among some that they don't need to take any responsibility for their own health, that they can just rely on the NHS to sort them out if it all goes wrong.