"Who has decided to place French and English on an equal footing on this document?" asked Helene Carrere d'Encausse, permanent secretary of the Académie Française.
The academy charged with defending the French language is threatening to take the government to court over the use of English on the country's new identity card.
The latest versions of the laminated cards that were introduced last year have included English translations of the different data fields, with "surname", "date of birth" and "expiry date" appearing next to their French equivalent in a slightly smaller, italic font.
Every French citizen is required to have a national identity card which they can also use as their main travel document when heading to another European Union country.
The addition of the English translations, therefore, appears to be a move to facilitate passage across international borders for French citizens.
But the venerable Académie Française, founded in 1635 under King Louis XIII to guard "pure" French, has taken offence and is threatening to mount a constitutional challenge over it.
"Who has decided to place French and English on an equal footing in this document?" asked Helene Carrere d'Encausse, the academy's permanent secretary.
"An essential principle is being jeopardised," she told the conservative newspaper Le Figaro, recalling that the modern French constitution provides in Article 2 that "The language of the Republic shall be French".
There is a European regulation requiring the words "Identity Card" to be translated into at least one other EU language, but Brussels leaves translating the rest of the document up to member states.
German national ID cards include translations into both English and French, while even passports issued by Britain — which quit the EU in 2020 — offer French translations.
Complaining that the academy's voice is no longer heard in public debate, the body has hired lawyers to write to Prime Minister Jean Castex, Le Figaro reported, "asking him to repeal the provision creating the new national ID card" — so far without receiving a response.
If Castex's office fails to reply, the lawyers are preparing to take the case to the Conseil d'Etat, France's top administrative court.
Bruno Retailleau, leader of the conservative Republicans group in the French Senate, tweeted Friday that "the new card no longer really has a 'French identity'. Why is there such insistence on erasing the substance of our pride and our national unity?"
The new card does feature the French flag with the outline of Mariane — the personification of the French Republic to represent the country's three main values liberty, equality, fraternity — and used since the Revolution as well as the words "République Française" written in bold characters.
Writer and musician Etienne Liebig, however, dismissed the Académie's crusade, telling broadcaster RMC: "Who are we French people to be so very afraid of losing our identity for reasons like this?"
The declining use of French worldwide has been a sore spot for the country for decades. French was for over 200 years the diplomatic language of choice. It remains spoken as a first or second language by an estimated 220 to 270 million people worldwide.
But the encroaching use of English in everyday life and on the geopolitical scene — especially within the EU since the departure of the UK, ruffles feathers.
French-speaking journalists covering the EU complained in 2020 about the increasing use of English in the bloc's official communication which they argued gave a competitive advantage to the anglophone press.
Perhaps sensing the controversy brewing, French President Emmanuel Macron and Ursula von der Leyen carried out their joint conference on France's six-month presidency of the EU on Friday entirely in French.
Clément Beaune, France's European Affairs Minister, said earlier this week that "the whole French presidency will be in French".
"The French language must find a place in Brussels," he added, announcing that the country had started training "many elected representatives from all countries in Europe, European diplomats, European civil servants, in French."
"We have to make people want to learn French, we have to make our culture shine, we have to train people in French," he stressed. "We are going to stop the decline of the French language."