The billionaire boss of the company behind brands such as Christan Dior, Givenchy and Louis Vuitton has laid into teen climate activist Greta Thunberg, accusing her of "demoralising" young people by embracing "catastrophism".

French businessman Bernard Arnault - the world's second richest man - made the comments at his own company’s sustainability event in Paris this week.

In the video above: PM hits back at climate change critics

The 70-year-old Arnault is worth $A161 billion and is now wealthier than either Bill Gates or Warren Buffet.

His company Louis Vuitton Moet Hennessy - known as LVMH - owns some of the world's most exclusive brands.

"She’s a dynamic young girl, but she’s surrendering completely to catastrophism," Arnault said at an event in Paris on Wednesday.

"I find that her views are demoralising for young people."

Arnault's comments came just days after Thunberg took aim at world leaders during a fiery speech to the United Nations in which she accused them of not doing enough to address climate change.

“We are in the beginning of mass extinction, and all you can talk about is money and fairy tales of eternal economic growth,” Thunberg said.

However, Arnault took issue with Thunberg's criticism of the ecomomic growth model which had lifted billions out of poverty and that Thunberg's criticism "offers nothing".

“If we don’t want to go backwards, we still need growth," he said.

"(Economic growth) has helped to improve world living standards, reduce poverty, improve health in countries like Africa. If we want to go back, stop growth."

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“I prefer positive solutions that allow us to get towards a more optimistic position,” Arnault added.

He also used the event to talk up LVMH initiaitves which included introducing processes around tracking raw materials to ensure sustainability and a reduction of CO2 emissions.

The company says is will obtain more than 30 per cent of its energy needs from reneweables by 2020 and cut CO2 output by 25 per cent at the same time.

With agencies.