France's richest man, Bernard Arnault, not only wants to become Belgian, he has moved a large part of his fortune north of the border, it was claimed on Thursday.

The billionaire head of the luxury goods group Louis Vuitton Moët Hennessy, who has applied for Belgian nationality, was reported to have transferred his share in the family group that controls LVMH to a firm set up for the purpose in Belgium, where taxes are lower.

A spokesperson for Arnault, 63, insisted he was not trying to escape the French taxman, but attempting to preserve the company in case he died suddenly. But the revelation reopened the controversy over Socialist president François Hollande's proposed "supertax" of 75% on earnings over €1m (£850,000) a year.

The high-rate tax, put on hold after France's constitutional court ruled it unfair and unconstitutional at the end of December, has been blamed for pushing a number of celebrated French citizens, including the actor Gérard Depardieu, into tax exile.

On Thursday there were also conflicting reports over whether Hollande would force through the controversial tax. Europe 1 radio reported the government had decided to "bury" the idea of a 75% band, a claim that was later denied by the Elysée Palace.

Nicolas Demorand, editor of Libération, which carried the story on its front page, lambasted Arnault for "forgetting the country which has made him a king". He said the businessman was "running the risk of fuelling suspicions about him which could harm the image of his brands and weaken the employees who bring them to life".

Libération claimed Arnault transferred his 31% stake in Groupe Arnault, a family firm that runs LVMH to a Belgian company called Pilinvest, in December 2011, six months before Hollande took office. That stake, the newspaper said, is worth €6.5bn.

Arnault was reported to have set up a foundation in Belgium, Protectinvest, which will take control of Pilinvest if he were to die before 2023. This would allow his five children, to whom he has already handed over a large percentage of shares in the family group, to be paid dividends but be prevented from selling their shares or exercising their voting rights. After 2023 the family would regain full control.

Sources close to the businessman, who insists he intends to keep paying taxes in France, said the move was intended to avoid damage to the group from family disputes over inheritance. However, inheritance tax in Belgium is only 3% compared with 11% in France, and Belgium has no wealth tax, unlike France.

Arnault's request for Belgian nationality has been turned down, but the final decision has yet to be made by the country's parliament.