Corsican pro-autonomy politicians were up in arms on Friday after a court banned the use of the Corsican language in the island's local parliament.

Based on France's constitution, a court in the Corsican city of Bastia ruled on Thursday that French was the only language allowed in the exercise of public office.

Corsican, which is close to standard Italian and has about 150,000 native speakers, is considered by the UN's cultural organisation UNESCO to be in danger of becoming extinct.

Thursday's verdict ruled the Corsican Assembly's custom of allowing Corsican language for debates was unconstitutional and therefore banned, the court said.

Beyond the language question, the court said that local rules effectively establishing "the existence of a Corsican people" were also a violation of the constitution.

The ruling follows a lawsuit brought by the prefect of Corsica -- the central government's highest representative on the island -- and comes as President Emmanuel Macron's administration is talking with local politicians about granting Corsica greater autonomy.

Leading pro-autonomy politicians immediately lashed out at the verdict.

"This decision amounts to stripping Corsican parliament members of the right to speak their language during debates," said the island's executive council president Gilles Simeoni and Corsican Assembly president Marie-Antoinette Maupertuis.

"Accepting this state of affairs is unthinkable for us," they said in a joint statement, announcing an appeal against the verdict.

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