A petition against a law to privatise La Poste has been launched by a coalition of left-wing parties.

"We must get millions of signatures to counter a terrible project which aims to reduce public services," said Socialist Party secretary François Hollande.

It was set up after a meeting between the socialists, the Parti Communiste Français and the Parti radical de gauche.

The petition will be circulating at the Fête de L’Humanité which takes place in Paris on September 12-14.

Unions have called for a national strike of postal workers on September 23.

The government plans to change the status of the group from an établissement public to société anonyme with a view to opening the company to private investment in 2010.