Paris (AFP) - Vivienne Westwood designer Andreas Kronthaler hit out Saturday at fashion's most powerful man Bernard Arnault for attacking Greta Thunberg.

The French billionaire and head of the LVMH conglomerate that owns labels like Louis Vuitton, Dior, Givenchy, and pop idol Rihanna's new brand Fenty, said the teenage climate activist was "surrendering to total catastrophism... that is likely to demoralise the young.

"She doesn't offer anything other than criticism," he told reporters in Paris earlier this week as he launched his group's new green drive.

The world's second richest man said he was strongly against "her extremely negative" stance.

"What we take from it is that we have to stop growth, which has reduced poverty, raised living standards and improved health in poor regions like Africa.

"If we want to go backwards, let's stop growth," he declared.

But Kronthaler, who is also Westwood's husband, called Arnault out after his Paris fashion week show for the label he now shares with Westwood, one of the pioneers of ethical fashion.

The "business as usual" attitude doesn't work anymore, he told AFP.

- 'Fashion is a big polluter' -

"We are sitting on a volcano, and on borrowed time. I am not a pessimist. I believe in the good of people. But it is crazy what we are doing. It's obvious and fashion is a very big polluter," he added.

Kronthaler praised Thunberg for giving climate change a "whole focus. I think the western world at least is waking up now. I think this young girl is terribly remarkable and we should thank her. I am very very glad that somebody exists like her."

The Austrian-born creator and his wife have long been environmental activists, with Westwood once telling AFP that she only takes a bath once a week to save water.

With supermodel Bella Hadid closing the show, Kronthaler sent out an elegant and highly original Mozart-themed collection made mostly from "forsaken fabrics from the best Italian mills".

Other material came from makers in Mali that the brand hooked up with through the Ethical Fashion Initiative, he said.

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Westwood and Kronthaler are among the leaders of fashion's "reduce, reuse, rethink" movement, sourcing unsold or off-cut high-end fabrics for their clothes.

"RuPaul's Drag Race" stars Aquaria and Violet Chachki were in the front row alongside Canadian actress Pamela Anderson to see both male and female models in skirts and dresses.

The charismatic Kronthaler has always featured men in his women's shows "because they can be just as beautiful as women in a dress", he insisted.

"It is very liberating for men to be able to wear anything, and now it is becoming much more of a reality in the street," the added.

Arnault, who has made the vegetarian British designer Stella McCartney his personal advisor on sustainable development, said that "he preferred positive solutions which allow us to keep an optimistic view of progress rather than fall into catastrophism."