He is known as the “wolf in cashmere” – the owner of the world’s biggest luxury group whose brands including Louis Vuitton, Dior and Tiffany have made him one of the world’s richest people.

But Bernard Arnault, a close friend of Donald Trump, is under fire from journalists’ unions in France for buying up almost all the country’s business and economic press.

Reporters Without Borders said Arnault had a “stranglehold” on the main business titles in France after his LVMH group bought the centrist business weekly Challenges.

LVMH, whose brands include fashion, perfumes, champagne and spirits, has an array of business publications including the leading economic daily paper, Les Echos, and the business information service L’Agefi.

Reporters Without Borders and journalists’ unions have filed two different complaints over the purchase of Challenges. France’s council of state is considering whether authorities failed to properly examine the scope of LVMH’s business media ownership, and the competition watchdog is considering union arguments that the group “abused its dominant position” by acquiring Challenges.

“This is a textbook example of the loopholes in French law which fail to keep media ownership in check,” said Laure Chauvel, the head of the France-Italy desk at Reporters Without Borders.

LVMH did not comment when approached by the Guardian. But Arnault, who also owns the daily newspaper Le Parisien and the celebrity magazine Paris Match, told a senate committee in 2022 that he bought media “in the general interest”, to protect key titles and keep them alive.

Arnault’s expansion comes amid growing debate over the handful of billionaires who dominate media ownership and are reshaping the news landscape before next spring’s presidential election. The far right is polling high as Emmanuel Macron’s two terms in office near an end.

The most prominent billionaire is Vincent Bolloré, the conservative industrialist who is close to figures on the far right. He has been accused of using his powerful media empire, including the TV channel CNews, to give a platform to reactionary voices. Bolloré’s large presence in book publishing and film production has also sparked a revolt by writers and film industry insiders. He has dismissed petitions against him and said he was a Christian democrat.

Other billionaires include Rodolphe Saadé, the head of the world’s third largest shipping company, CMA CGM, based in Marseille. His growing media empire includes the rolling news channel BFM TV, the Marseille paper La Provence, the weekly La Tribune Dimanche, and La Tribune, a former business paper and now online publication which was once owned by Arnault. Journalists at La Tribune went on strike in April expressing fears for its future after a plan to move staff to a new digital arm of the group.

The Czech energy billionaire, Daniel Křetínský, who owns the parent company of the UK’s Royal Mail, is also building a French media and publishing empire. Xavier Niel, the telecoms billionaire whose partner is the chief executive of Christian Dior Couture and Arnault’s daughter, Delphine, was Le Monde’s main shareholder until he placed his stake into a trust. On a smaller scale, the Dassault family, which runs the defence company Dassault Aviation, owns the daily Le Figaro.

But Arnault, whose fortune is estimated by Forbes magazine to be around $145bn (£108bn), is by far the richest, highest profile and biggest business leader to own media in France. Born into an industrial family in the northern town of Roubaix, he began his career in construction and real estate. In 1984, he lobbied the French government to let him take control of a near-bankrupt textile company, Boussac, which owned a brand he wanted: Christian Dior. After decades of acquisitions, LVMH is the world’s most valuable luxury group.

Arnault’s clearest political stance has always been his opposition to wealth taxes. In the early 1980s, the young Arnault briefly moved to the US to avoid what he saw as the left’s hostile business environment and the socialist president François Mitterrand’s tax on the rich. While there, he cultivated a close friendship with another real estate figure, Trump.

Arnault, his wife and two of his children were the only French guests on the platform at Trump’s second inauguration as US president in January last year. Arnault said after that he had witnessed “the winds of optimism” in the US and returning to France was like a “cold shower”. He spoke out last year against calls by the left for a 2% wealth tax on all assets. He told the Sunday Times that such a move would be “deadly for our economy”.

In April, Arnault was among several top French business leaders reported to have had dinner with Marine Le Pen, of the far-right National Rally (RN). Le Pen’s party, polling high, is gaining more access to business leaders who once shunned it but now want to be heard on policy. The same month, Paris Match, owned by Arnault, ran a cover story on the RN’s potential presidential candidate, Jordan Bardella, strolling hand-in-hand with his girlfriend, Princess Maria Carolina de Bourbon des Deux-Siciles, in what was seen as a pre-election attempt to soften his image.

Journalists at Challenges and Les Echos are seeking to ensure they can keep the charters protecting their independence, which they fear is uncertain. The Challenges charter defines its centrist approach to business reporting as social, humanist and progressive, but there are fears Arnault prefers a more resolutely free-market approach.

Unions said Arnault’s group had not yet signed the Challenges charter which, unless renewed, expires next year. Les Echos’ charter is also up for renewal in 2027. Both titles have held unprecedented strike action. In 2023, journalists at Les Echos protested after the departure of their editor and management’s move to replace him.

“Bernard Arnault has in a few years effectively helped himself to the best part of the business press,” said Alexis Lévrier, a media historian at the University of Reims. “He has a near monopoly on economic news.”

Lévrier said Macron, despite election promises, had failed to legislate on media ownership and protections. He said he felt the president feared business leaders such as Bolloré or Arnault: “There is no equivalent in French history of this reversal of the relationship between economic power and political power. Economic power, which owns media, can impose its views on the political power in place.”

In 2022, senators asked Arnault about his attitude to the media. He admitted pulling advertising from the leftwing daily Libération in 2012 after it ran what he called an “aggressive” and “wrong” front page on his alleged desire to flee to Belgium to avoid tax rises. Arnault said he called the Libération editor to complain, and the advertising spend on the paper was in any case very small. He denied pulling advertising from Le Monde in 2017 because it had named him in Paradise Papers reporting on offshore tax havens.

Senators interviewing Arnault also referenced the trial of the former head of France’s domestic security services, Bernard Squarcini. One part of the charges against Squarcini related to an alleged scheme to spy on the former journalist and now MP François Ruffin while Ruffin was making a documentary about LVMH. The company paid €10m (£8.6m) in 2021 to settle the allegations it faced in the case, without any admission of wrongdoing. Arnault told a court hearing he had been “completely unaware” of the alleged scheme, and he told senators he rejected any culpability. Squarcini is appealing against his guilty verdict.

Sophie Taillé-Polian, a Green MP who worked on a bill aimed at safeguarding media pluralism by limiting the concentration of media ownership, said it was disappointing that, despite a consultation, no law had been passed under Macron. “When we have a domain as important as the business press under the care of one of the wealthiest people in both France and the world, that raises questions,” she said.