NOTRE-DAME-DES-LANDES, France (Reuters) - Environmental activists living in cabins and tree houses on the site of a proposed new airport outside Nantes in Western France braced on Wednesday for a looming showdown with security forces after the prime minister said clearing the zone was a priority.


Opponents of the Aeroport du Grand Ouest say the 580 million euro ($637 million) project is too costly, will damage the environment and is unnecessary given Nantes already has an airport. They count ecologists, anarchists, punks and communists among their ranks.


The development has stoked tensions within the Socialist government six months ahead of a presidential election, with Environment Minister Segolene Royal leading calls for the airport to be scrapped.


However, Prime Minister Manuel Valls said he would press on with the project after people in the Loire-Atlantique region voted in favor of the scheme in June.


The project has been on the drawing board for more than four decades and there have been violent confrontations in past years when riot police tried to clear protesters out.


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(Reporting by Guillaume Frouin; Editing by Richard Lough)