Medical charities which campaign for expensive new drugs receive millions of pounds of funding from the pharmaceutical industry, a Sunday Herald investigation can reveal.

One charity, Arthritis Care, has admitted that the pharmaceutical giants Pharmacia and Pfizer fund their latest campaign, which calls for the wider prescription of a new class of drug which they make called COX-2 inhibitors. But the charity refuses to say how much cash it received.

Health experts say the benefits of the expensive new drug have been exaggerated. Results of a trial, funded by Pharmacia, showing the new drug is safer than those they would replace, have been disputed in medical journals.

Another charity, Diabetes UK, has admitted that last year it received about £1 million from the industry while the national health watchdog, the Patients Association, receives up to 20% of its funding from pharmaceutical companies.

But funding from the industry to charities is often kept secret. Now t he extent of the funding has prompted leading medical experts to call for all sums to be made public.

Dr Simon Maxwell, senior lecturer in clinical pharmacology and therapeutics at Edinburgh University and a doctor at the city's Western General Hospital, said: 'The pharmaceutical industry do this because they realise that the people who can really have the strong political message are the patient groups.

' The pharmaceutical industry knows that this is the lobby that has the power with the government and health professionals.

'This causes great concern. As a doctor involved in new drugs I have to declare all of my interests when I state an opinion about a drug. If I travelled anywhere funded by the pharmaceutical industry then, quite rightly, I would need to declare that. So, if these patient bodies state their opinions, and they are perfectly entitled to do that, they should make the same declaration that they have an interest in this.'

Professor Warlow, professor of medical neurology in the department of clinical neurosciences at Edinburgh University, added: 'Medical charities are an increasingly important source of advice and information for patients and, if a company can influence that advice, then of course it may try to do so.

'I have no idea how much all this actually does influence charity and medical advice, but presumably the more money that is provided, the more the advice could be changed.

'That is why I, and others, are keen to see exactly how much money is involved in research grants, consultancy fees, and 'educational' meetings.'