His story has parallels with that of Erin Brockovich, whose David-and-Goliath battle against a United States energy company became the subject of a Hollywood film.

But unlike the American legal clerk, Liam Grant is taking on a giant pharmaceutical company.

In 1996, Grant's 19-year-old son, also called Liam, was prescribed Roaccutane, an acne drug. Formerly cheerful and outgoing, he soon became withdrawn and reclusive. Four months after he started taking the drug, he was found hanging from a tree outside Dublin. A jury delivered a verdict of suicide.

Grant has spent more than €1 million ($1.74 million) of his own money pursuing the drug's manufacturer, the Swiss company Roche, and the regulators whom he holds responsible for his son's death. Roche denies it is to blame for any deaths or severe mental health problems.

He has now won a crucial ruling from the European Ombudsman, Nikiforos Diamandouros, that the European Medicines Agency should release details of all adverse reactions to the medicines it licenses.

It is required to respond by July 31. If it complies, patients will for the first time have access to Europe-wide details of suspected adverse reactions to all medicines licensed by the European Union's drug safety body.

A forensic accountant from Dublin, Grant was supported by his wife, Loyola, and their three surviving children in investigating Roaccutane. When he could not persuade the company to carry out the studies he thought necessary, he funded them himself.

In 2004, he sued Roche in the Irish courts. The company responded by offering to pay him the maximum compensation under Irish law for the death of his son - about €30,000 - as well as his costs and special damages.

When he refused, Roche appealed to the Irish Supreme Court to compel him to accept. In 2008, the court threw out the appeal and ruled that his case could go ahead.

A scientist hired by Grant to investigate Roaccutane found that despite the number of studies suggesting a link with depression and suicide, at the time only a handful of countries required that the drug carry warnings to this effect.

Warnings were subsequently added in all countries and last year Roche withdrew Roaccutane from the market. The company said the decision was made for business reasons.