There is growing concern that patient groups and health charities should be more transparent about their funding given that they are widely perceived to be independent, according to a special report on thebmj.com today.

Charities often campaign for access to newly licensed drugs for their patients without making clear enough that they receive funding from the drug companies who make them, journalists Sophie Arie and Chris Mahony say.

As an example of the problem, they point out that MS charities who protest that NICE is denying patients 'life-saving' drugs such as Sativex have also received funding from Bayer which markets Sativex. NICE is due to confirm its decision on that drug when publishing its updated guidance on the treatment of MS next week (Oct 8).

But, while the Association of British Pharmaceutical Industries (ABPI) requires drug companies to disclose all the details of their relations with patient groups and charities on their websites, UK charities are not legally required to name all their donors.

Most charities have policies on working with industry that include a limit on the proportion of total income received from corporate donors and avoiding receiving donations from only one company.

So does it matter if charities fail to mention their corporate donors when campaigning in favour of the drugs they make, ask Arie and Mahony?

They point out that patient groups have gained influence in recent years. "As government has become more keen to work with stakeholders, their potential to influence policy has grown," they write. Yet little research has been done into how health charities are funded and how transparent they are about that funding.

Jeremy Taylor, chief executive of National Voices, the national coalition of health and social care charities in England, says when a charity advocating for groups of patients takes money from a pharmaceutical company, "there is the risk of allowing your charitable objectives to be distorted to serve the interests of commercial organisations or simply being seen as serving the commercial need of the other organisations."

Arie and Mahony point out that there have only been a few reported cases of charities' activities being clearly compromised by their relations with a drug company and there is no reason to suspect that this is widespread. But the few cases that have come to light, "have fuelled concern over a need for a culture of full disclosure throughout the sector, which could help patient groups avoid unintentionally giving credibility and sincerity to a drug company's agenda."

Opinions are divided within the health charity sector between those who take drug company support - and are adamant their donors wield no influence - and those who believe that to preserve their reputations health charities need to be much more transparent about their relationships with industry, they write.

Some, such as the mental health charity MIND, go so far as refusing any support from industry while others believe what's needed is clearer guidelines for all health charities to adhere to.

Jeremy Taylor has recently begun working with the ABPI to produce a joint guide on collaboration between industry and patient groups, covering the importance of governance, protecting independence, transparency, income diversity and what to think about when entering an arrangement with a pharmaceutical company.

At an international level, the International Alliance of Patients' Organisations (IAPO) acknowledges there is a problem, but say it can only advise its members on best practice, it cannot force them to comply or impose any sanctions if they don't.