Martine Aubry, a leading French politician who led the ruling Socialist party, was Friday cleared by an appeals court of manslaughter in a probe into thousands of deaths caused by exposure to asbestos.

The court's decision clears the way for Aubry, who was charged with manslaughter in November, to return to top-level politics. She stood down as Socialist leader last year.

Aubry is now free to bid for a seat in President Francois Hollande's government. She had stood against Hollande in the primary to become the party's presidential candidate last year on a slightly more left-wing platform.

"The courts today recognised that no fault or negligence could be attributed to me," Aubry, who is presently the mayor of the northern city of Lille, said in a statement.

"Everybody knows that I have always acted as an official and as a minister to defend and reinforce the rights of workers and protect them from occupational hazards," she said.

The case against Aubry relates to her time as a senior official in the ministry of social affairs, before she became a major figure in French politics.

As the ministry's director of industrial relations from 1984-87, Aubry is accused of having helped to delay the implementation in France of a 1983 European Union directive designed to strengthen the protection of workers dealing with asbestos.

The examining magistrate in the case said Aubry bowed to pressure from industrialists lobbying against a complete ban on the use of the material and that she ignored warnings from French health authorities of a mushrooming epidemic of cancers and terminal lung diseases.

Aubry, the daughter of former European Commission President Jacques Delors, was one of many figures caught up in a far-reaching probe into how the French authorities handled the emerging evidence of the dangers posed by asbestos between 1970 and 1997, when the material was finally banned.

The specific charges against her related to the case of workers employed at the Fereo-Valeo auto-components factory in Normandy. Asbestos was once widely used for car brake pads.

An estimated 3,000 people currently die prematurely every year in France as a result of asbestos poisoning and there have been pessimistic predictions that the death rate could nearly treble over the next decade because of exposure in the 70s and 80s.