Laurent Fabius, Socialist Prime Minister from 1984 to 1986, and his colleagues are accused of being responsible for seven people contracting Aids from blood transfusions contaminated with the HIV virus. Five of the seven have since died.

The BBC's Stephen Jessel: "There are no precedents for this trial in recent French history"

The BBC's Paris Correspondent, Stephen Jessel, says the trial is unprecedented in French post-war history.

Four health officials have already been convicted in previous trials but this is the first time the courts are judging the accountability of top government officials.

'Crucial delays'

Laurent Fabius: One of France's most prominent politicians

The charges against the three vary. Mr Fabius is accused of delaying the introduction of a US-made blood screening test until a French competitor was ready.

His two former colleagues, former Health Minister Edmond Herve and former Social Affairs Minister Georgina Dufoix, are accused of failing to introduce a scheme to heat blood, a process which destroys the virus.

They are also accused of failing to stop the collection and distribution of blood which was known to carry risk of contamination.

Hugh Schofield in Paris: "Laurent Fabius continues to protest his innocence"

The prosecution claims the US company Abbott Laboratories invented a test, which was available in March 1985, which enabled blood to be tested for HIV.

But it was not until 1 August 1985 that systematic testing of blood donors went into effect in France - on Mr Fabius' orders - using a test made by the French company Diagnostics Pasteur.

Unprecedented trial

The Court of Justice of the Republic, a special tribunal which allows politicians to be tried by their peers, is meeting for the first time. Its judges are made up of three professional magistrates and 12 deputies and senators, seven of them from parties hostile to Mr Fabius, who is now Speaker of the National Assembly.

The seven cases at the heart of the trial are only the tip of the iceberg.

Olivier Duplessis, president of the French Association of Transfusion Recipients: "The whole country wants an explanation"

Around 4,000 French people, many of them haemophiliacs, have died of Aids after receiving transfusions of blood carrying the HIV virus.

In 1991 an experts' report found that of the 4,000 who contracted the virus, 300 were "avoidable".

Olivier Duplessis, whose father and mother contracted the HIV virus after a transfusion, is president of the French Association of Transfusion Recipients.

He says the whole of France wants an explanation of how the tragedy was allowed to happen.

Political and legal reverberations

The trial, expected to last at least three weeks, has profound political, legal and moral implications, including the question of ministerial responsibility.

It is the first time since World War II that French ministers have gone on trial for their official acts.

The defendants served under the late President Francois Mitterrand in the mid-1980s, a time when the dangers of Aids as a modern-day plague were surfacing for the first time.

All three say they never knowingly approved the use of contaminated blood products in transfusions.

'I am innocent'

Ms Dufoix said recently: "In my soul and conscience, in the deepest part of my being and before God, I do not feel guilty."

Sylvie Rouy, one of the two Aids-infected survivors named in the case, told Libèration newspaper: "These people had a duty toward us.

"Why did they not hesitate to put industry first, to the detriment of public health? They played with my life."