Fashion designer Karl Lagerfeld was in hot water on Friday after calling French President Francois Hollande an "idiot" over his plans to impose huge taxes on the rich.

Hollande's former companion and a one-time presidential contender Segolene Royal led the charge, saying the Paris-based German designer must apologise immediately.

"There is no place for insults, especially from a designer who benefits from the image and prestige of France," Royal said on RTL radio.

"When one is working in the French luxury sector, one enjoys the collective backing of the entire nation and these insults are absolutely misplaced," she said.

"I hope he will apologise."

Lagerfeld in an interview to the Spanish edition of Marie-Claire called Hollande -- who famously said he does not like the rich -- an idiot for imposing a 75 percent tax on incomes exceeding one million euros ($1.3 million) annually.

"This idiot will be as disastrous as Zapatero," Lagerfeld said, referring to Spanish former prime minister Jose Luis Rodriguez Zapatero whose term witnessed the country's economic bust.

"Hollande hates the rich. That is disastrous. He wants to punish them and obviously they will flee and no one will invest."

Lagerfeld, the quirky creative director of French fashion house Chanel, also took a swipe at French products, saying they were not marketable.

"Apart from fashion, jewellery, perfumes and wine France is not competitive," he said.

"The other products do not sell. Who buys French cars? Not me," he added.

[Image via Agence France-Presse]