The UK’s largest doctors’ union has signed the AllTrials register, putting more pressure on other pharma and medical groups to follow suit.

The British Medical Council is backing the AllTrials campaign, which wants all trials registered and all results reported, to ensure that decisions about treatments are informed by the best information available. Evidence suggests about half of all clinical trials data has never been published.

The BMA director of professional activities, Dr Vivienne Nathanson, said: “The BMA has signed up to the AllTrials petition because doctors need accurate and unbiased information on the efficacy and safety of different treatments. This helps them prescribe properly and safely for their patients.”

She pointed out that if data from clinical trials was withheld or otherwise not available doctors could not be sure of the risks and benefits of using particular drugs. This could risk avoidable harm to patients and be a waste of scarce resources.

Dr Nathanson added: “Under-reporting also betrays the altruism of research subjects, who participate in clinical trials in the expectation that the risks they undertake will help to advance medical science and benefit society. Where results go unreported there is also a risk that research will be repeated unnecessarily.

“Access to full clinical trial information also allows researchers to identify and investigate specific questions of importance and to improve study designs to achieve better results, which in turn benefits patients.”

AllTrials was launched by the BMJ – the organ of the BMA - in conjunction with Sense About Science, the James Lind Initiative, the Centre for Evidence-based Medicine and Ben Goldacre’s Bad Science campaign.

The union follows recent signatories GlaxoSmithKline, NICE and 80 UK-based patient groups, who are all calling for greater transparency when reporting clinical trial results.

But as yet, only one pharma firm in the guise of GSK has signed up to the register, with all other pharma firms, and the UK lobby group the ABPI, refusing to sign up, deeming it a “PR initiative”.