Scientists say data must be released to allow the true benefits and harms of drugs to be independently assessed

The body that licenses medicines in the UK and Europe is today accused of putting commercial interests ahead of the safety of patients after two scientists battled for three years to get access to unpublished trial data.

The European Medicines Agency (EMA), which is responsible for the safety and efficacy of medicines licensed in Europe, only released the trial findings, running to almost 130,000 pages, in February after the European ombudsman ruled that it was guilty of maladministration.

The scientists, from the Nordic Cochrane Centre in Denmark, say the withholding of unpublished data puts the lives and welfare of patients at risk and full access must be granted to allow the true benefits and harms of drugs to be independently assessed.

Pharmaceutical companies invest millions of pounds in drug research and have a powerful commercial interest in publishing positive findings for the medicines they have spent years developing.

This is known as "publication bias" – the selection of only positive studies for publication. Publication bias has been blamed for the debacle over the powerful painkiller Vioxx, which was withdrawn from the market in 2004 over fears that it could cause heart attacks. Professor Peter Gotzsche and Anders Jorgensen from the Danish Cochrane Centre said Vioxx "has probably caused about 100,000 unnecessary heart attacks in the US alone" as a result of selective reporting.

They decided to investigate two obesity drugs, orlistat and sibutramine, and requested the unpublished trial data from the EMA in June 2007.

"Anti-obesity pills are controversial," they said. "People have died from cardiac and pulmonary complications or have experienced psychiatric disturbances, including suicidal events."

Sibutramine was withdrawn from the market in January 2010 following evidence that it increased the risk of heart attacks and strokes. Another obesity drug, rimonabant, was also withdrawn. Orlistat is the only one that remains on the market.

But the EMA refused access to the data, citing commercial confidentiality. The regulatory body argued that they constantly monitored drugs and updated their assessments.

In June 2010, the European ombudsman, Nikiforos Diamandouros, criticised the EMA's refusal to grant access to the trials and said it was guilty of maladministration. The EMA responded in November, saying it would widen public access to trial reports and other documents. But it did not release the data on the obesity pills to the researchers until 1 February 2011.

Professor Grotzsche said yesterday that they had not yet had time to study the unpublished trials they had received.

Writing in the British Medical Journal, the authors say the case sets a precedent on the transparency of data, and other regulators such as the Food and Drug Administration in the US should follow suit.

The EMA said it had released 129,303 pages of documents to the Cochrane researchers in line with its "access to documents" policy which came into force last November.