The Swiss euthanasia group Dignitas, which claims to offer a dignified death to terminally ill people, is being investigated after a healthy German woman was given a lethal mix of drugs by providing a false medical report.

Dignitas has helped 453 terminally ill Europeans, including 30 British people, to end their lives since it started in 1998. Assisted suicide is legal in Switzerland, but of the groups registered to provide such assistance only Dignitas offers its services to foreign nationals, and it recently opened its first office abroad in Germany to recruit clients (BMJ 2005;331:984, 29 Oct).

In the incident under investigation a 69 year old woman, who has not been named for legal reasons, approached Dignitas with a medical report showing that she had terminal liver cirrhosis and was given a lethal dose of sodium pentobarbital drugs.

But a routine autopsy carried out by German authorities when the body was brought back from Switzerland exposed the report as a fake and added that although the woman had depression she was nevertheless physically fit.

The doctor used by Dignitas to help administer the lethal injection has also died. He committed suicide shortly after he was told that the German woman had not been terminally ill.

A subsequent investigation found that she had persuaded her GP in Augsburg to falsify the report by telling him she needed the report to get sick leave from work. The doctor told police he had no idea the woman would use it to persuade Dignitas to help her commit suicide.

Hans-Juergen Kolb, Augsburg’s senior public prosecutor, confirmed that the investigation included the German GP and the 71 year old Swiss doctor as well as Dignitas itself, although after the death of the Swiss doctor charges against him would be left on file once the report for prosecutors was completed.

He said, "At the moment the investigation is in its early stages, and we are cooperating with the Swiss authorities. Autopsy reports have already shown that the woman was not suffering from irreversible liver damage."

The death will strengthen critics’ claims that Dignitas has been promoting "suicide tourism" and making money from people’s suffering, especially in Germany, where the Dignitas office was recently opened in Hanover.

Lower Saxony’s justice minister, Elisabeth Heister-Neumann, said, "Making poisonous cocktails available has deviated into pure business, and medical reports are being sanctimoniously misused as an excuse."

But the founder of Dignitas, Ludwig Minelli, defended his organisation: "The doctor’s report that I was given indicated the woman was suffering from cirrhosis of the liver as well as hepatitis. And in any case every person in Europe has the right to choose to die, even if they are not terminally ill."

He also rejected critics’ suggestions that his organisation was driven by financial concerns rather than altruism. He said, "Members’ fees and donations cover the costs of running the organisation and providing care and counselling for those who need it. We also put money into developing palliative care methods; we do not profit from our work as individuals."