New guidelines on NHS sponsorship issued by the Department of Health (DoH) could lead to the termination of contracts worth millions of pounds between health trusts and outside companies. The guidance lays down a number of principles for future sponsorship arrangements but the bottom line is clear: outside money should never dictate what is best for the patient.

And it goes on to warn that any existing sponsorship contracts that fail to meet these standards should be renegotiated.

That move could be accompanied by the sound of the ripping up of contracts across the NHS because it is clear that the central motivation for much health sponsorship is to get preferential treatment for a particular company's product.

In stoma care, for instance, more than 60% of the country's 600 stoma nursing posts are now financed by the stoma care companies.

The nurse will still be employed by the trust but the contracts will offer the company some tangible benefits in return for its investment - an investment which can be worth as much as £100,000 each year.

Some contracts, for instance, stipulate that a certain proportion of patients treated should be fitted with the sponsoring company's stoma bag.

That proportion is often more than 50%. That can be very big money indeed for the manufacturer since once a patient is fitted with a bag they may be using that product - along with a range of accessories - for life.

Julia Breeze, who chairs the Royal College of Nursing gastroenterology and stoma care nursing forum, recalls how when she was a sponsored stoma nurse, the sponsoring company complained that only 30% of her patients were going home with the company's products and that the figure must be increased.

She resisted successfully, but has no doubt other nurses are put under similar pressures and that in some cases they succumb.

The other common way in which sponsoring companies can recoup their investment is by inserting a clause in the contract that stipulates they should be the sole dispenser of any stoma care equipment to the patient in their home.

This may be small print but it is big business because it entitles them to 25% of the cost of each item dispensed - money that the NHS forks out on top of the cost of the product.

The new guidelines suggest this would no longer be acceptable and says such clauses should be urgently renegotiated.

Although Ms Breeze remains uneasy about sponsorship, she says stoma services cannot survive without it. "We are a very expensive commodity and the money isn't there for us otherwise - there are so many competing needs in the NHS these days," she said.

Stoma care nursing may be the biggest target for sponsorship but it is by no means the only one.

Continence care and a number of chronic conditions such as Parkinson's, MS and inflammatory bowel disease have attracted the attention of manufacturers and drug companies who can see big advantages in teaming up with clinicians.

RCN nurse adviser Susan Scott believes the pressures are likely to increase now that nurses have some prescribing powers. The only way forward is to be completely open about the process and to be clear the patient's interests must always come first.

"The absolute bottom line is that any nurse has got to use her clinical judgement knowledge and skill to ensure that the product or service is the right one for that patient," said Ms Scott.

British Healthcare Trades Association director Ray Hodgkinson says the industry probably now regrets ever having got involved in sponsorship in the first place.

"If a company goes into sponsorship it must be trying to influence its sales," he said. "But the problem is it can create issues of conflict of interest between commercial and clinical considerations."

So might they start backtracking? That's not easy, says Mr Hodgkinson, partly because many sponsorship deals have been initiated not by the companies but by the NHS itself.

Indeed he is aware of many tendering processes where trusts ask the bidders to propose sponsorship tie-ups as part of their tender.

It all shows just how complex the world of health sponsorship has now become - and how difficult it is going to be to disentangle.