French environmentalists voiced outrage on Thursday after the government admitted it was mulling plans to slaughter more than half a dozen wolves to prevent the creatures from ravaging sheep.

A "Wolf Action Plan" being studied by the government suggests that between five and seven wolves should be slaughtered to protect flocks in the Alps, the mountainous southeast of the country.

Wolves became re-established in France about 12 years ago, when a small group crossed over from Italy.

There are now between 37 and 55 of them, according to the various estimates.

French shepherds are demanding a big cull, saying their livelihoods are at risk.

Even though they are entitled to compensation if a sheep or lamb is devoured by wolves, some have been taking the law into their own hands, shooting at wolves or poisoning them.

The Society for the Protection of Animals (SPA) warned Thursday that France's wolves could get "wiped out" by loss of genetic diversity if seven were killed.

Aspas, an association for the protection of wild animals, vowed to file a suit against the government for breaching laws on endangered species if it pushed ahead.

Ecology Minister Serge Lepeltier told reporters he had yet to decide on a course of action.

Agriculture Minister Herve Gaymard, facing France's powerful farming lobby, has spoken out several times in favour of a cull.