Servier and its president are on trial in France, charged with misleading patients and health authorities about a weight loss drug.

Mediator (benfluorex), widely prescribed as an appetite suppressant, is believed to have caused over 500 deaths by heart valve failure.

The drug was withdrawn in France a decade after its withdrawal on safety grounds in Spain, Italy and the US.

Servier is accused of misleading French doctors about the risks of Mediator, whose prescription was supported by a government subsidy.

In addition to the criminal charges, several hundred civil plaintiffs are seeking damages of €100,000 each.

Servier’s President Jacques Servier, aged 90, and four other executives risk prison sentences of up to four years.

A second French trial, dealing with allegations of negligence and corruption, may follow.

Mediator, originally developed as a diabetes drug, was taken by up to 5 million people in France between 1976 and 2009 to assist weight loss.

The alleged failure of the French healthcare regulator to investigate the drug’s risks has prompted comparisons with the PIP implant scandal.

As with that case, the Mediator scandal has prompted questions about safety regulation at EU level.

Lawyer Charles Joseph Oudin commented: “Servier let people use a toxic product for years. There is no debate about it.”

The Chair of the European Medicines Agency’s committee for approving new drugs has resigned suddenly with immediate effect.

Dr Eric Abadie, who has led the Committee for Medicinal Products for Human Use (CHMP) since 2007, stood down after his position at the French healthcare regulator AFSSAPS was questioned.

The regulator has come under scrutiny for allowing the continued sale of Mediator after it had been withdrawn for safety reasons elsewhere.

Concerns have also been raised about the Agency following the controversy over breast implants manufactured by French firm PIP.

Dr Abadie noted in his public declaration of interests with the EMA that he had no links to any pharmaceutical company or health organisation. However, a spokesman said his decision was related to his position at the AFSSAPS, where he works as a scientific advisor to its Director General.

A spokesperson for the EMA said an election for a new chair for the CHMP would happen in “due course”.

In the meantime, Dr Tomas Salmonson, currently the vice-chair of the CHMP, will lead the Committee to ensure a continuity of operations. The next meeting is scheduled for April 16-19.

The EMA is under investigation by the European Anti-Fraud Office (OLAF) over alleged conflicts of interest.

The investigation was raised by Michèle Rivasi, a French Member of the European Parliament, who claims independent oversight by the EMA is impossible due to the majority of its budget coming from pharma.

OLAF told The Independent the investigation opened in July, but “for reasons of judicial secrecy", could not give any further details.

It’s believed the inquiry relates to the Servier’s controversial diabetes drug Mediator. The medication was withdrawn from the European market in 2009, ten years after concerns were first raised the treatment may be responsible for fatal heart problems.

Mediator was on the market for more than three decades and was used as a weight loss drug taken by an estimated 5 million people in France alone, plus countless more in Italy and Spain. It is estimated the drug caused up to 2,000 deaths during its time on the market before it was withdrawn.

The fallout from the scandal saw the French regulator, the Health Products Safety Agency, overhauled and its chief executive resign after an official report found it had “failed in its duties”.

The EMA was formed back in 1995 to provide a collective voice on drug regulation systems in the EU. The Agency has been attempting to its transparency with a series of new working principles and said in October it had “strengthened the rules on how it handles potential conflicts of interest of its staff and experts" after criticism by the Budgetry Control Committee.

A spokesman for the Agency said it was aware of the inquiry but had yet to see any allegations. “We have a robust process for dealing with conflicts of interest. It is transparent and there's no attempt to hide anything,” he said.