More than 100 writers have quit the historic French publishing house Grasset in protest at its conservative billionaire owner, Vincent Bolloré, whose media empire has been accused of promoting reactionary and far-right ideas.

In an unprecedented walkout, dozens of writers including the acclaimed punk feminist novelist Virginie Despentes and the philosopher Bernard-Henri Lévy, signed an open letter against Bolloré, 74, who is close to far-right figures.

“We refuse to be hostages in an ideological war that seeks to impose authoritarianism everywhere in culture and the media,” they wrote. “We don’t want our ideas, our work, to be his property.”

Writers who signed the letter included Vanessa Springora – whose award-winning bestseller Consent, recounting how she was groomed by a French novelist as a teenager, became a major film – as well as the novelist Laurent Binet.

The writers said they would also take legal action to recover rights to their earlier work. Grasset has been home to some of the biggest names in French literature.

The protest was sparked by the departure of the Grasset editor Olivier Nora, who had run the imprint for 26 years and was seen by writers as the last rampart against reactionary ideas. Nora’s departure was understood to have been forced.

Although no explanation was given publicly, it had been widely linked to the acquisition of the next book from the conservative French-Algerian novelist Boualem Sansal.

The journalist and writer David Dufresne tore up his Grasset contract on a TV chatshow, saying: “Bolloré is trading in commerce and ideology, not literature or essays.”

The mass walkout comes months after independent booksellers across France warned of the growing influence of Bolloré, whose vast cultural empire includes television, radio and the Sunday paper Le Journal du Dimanche, which is now seen as a platform for the far right. In 2023, Bolloré’s organisation took over the biggest book publishing and distribution conglomerate in France, Hachette Livre.

Bolloré is best known in France for his group’s ownership of CNews, which last year was the most-watched news channel on TV. Figures on the left have attacked CNews for giving a platform to reactionary voices they say have aided the rise of the far right. The Paris prosecutor’s office this month opened a legal investigation into racist comments on the channel against the mayor of Saint-Denis, Bally Bagayoko. The channel denied racism.

Bolloré, a Breton industrialist, was once described by the former education minister Pap Ndiaye as “very close to the most radical far right”. In a senate hearing in 2022, Bolloré denied political or ideological interventionism, saying his interest in acquiring media was purely financial and his cultural empire was about promoting French soft power. He said his group was so vast, it contained all views.

But since Bolloré’s vast expansion into publishing, writers and independent booksellers have said it is dangerous for democracy for one conglomerate to have such a huge influence on cultural output. Hachette Livre, which was part of the Lagardère group bought by Bolloré’s Vivendi in 2023, is the biggest publisher and book distributor in France. It owns scores of publishing houses, producing the bestselling Asterix comic books, literary fiction, thrillers, political titles, Manga comics and school textbooks. The group also owns the Relay bookstores at French train stations. Hachette has more than 200 publishing imprints worldwide. It is the second biggest publishing conglomerate in the UK, where it owns Hodder & Stoughton, and is the third biggest in the US.

Fayard, another historic publishing house now part of the Bolloré empire, has become home to a roster of far-right authors, from the potential presidential candidate Jordan Bardella to the anti-immigration businessman Philippe de Villiers.

The writer Colombe Schneck, who was key in organising the open letter, said writers of very different backgrounds on the right and left had joined the protest. She told Agence France-Presse: “We can’t let all the publishing houses of the Hachette group become far-right.”

Hachette has not commented.