The humble foodstuffs had their catwalk debut at the Ethical Fashion Show, now in its third year, where more than 60 designers from around the world gathered over the weekend.

Among the exhibitors was Les Racines du Ciel, a small clothing manufacturer based in the Brittany region of France that has used the humble sweet potato to give a traditional Chinese flavour to Western fashions.

"In southern China and only in southern China, silk is lacquered with a sweet potato paste and then buried in the ground," says Natalie Goyette, the company's development director.

"Then the silk is rinsed up to 30 times, and comes out with a soft off-black color that I find beautiful."

But Goyette says that her work was not simply about clothing.

"Maybe I am too idealistic, but I want to change the world," she added, "to make it a better place, environmentally speaking."

Leafy

"Bamboo is used instead of cotton by a growing number of designers because it has what industry people call great drape"

Summer Rayne Oaks, fashion consultant

At another stand, Grace Trance, who owns her own label based in San Francisco displayed a skirt made of pineapple fibers, called pina cloth.

The skirts are a yellow colour but do not come from the fruit itself, but rather from the pina leaves.

"The tradition comes from the Philippines," Trance says, "where the leaves are used to make barong shirts."

"The leaves are softened and the fibers are stripped from them. I'm the only designer at this show using pina leaves."

Another material currently in the ethical spotlight is bamboo.

"Bamboo is used instead of cotton by a growing number of designers because it has what industry people call great drape, meaning it fits perfectly on human bodies," says Summer Rayne Oaks, an ethical fashion consultant who has written extensively on bamboo.

Giant meddling

Ethical fashion falls into two parts: using organic materials such as cotton, silk, bamboo and hemp, and ensuring that the garments are made in way which puts mostly women in non-exploitative, labour-friendly structures in African countries or elsewhere in the developing world.

Industry consultants attending the show said they aimed to ensure that the bulk of manufacturing will continue to be done by small companies, rather than by clothing giants increasingly jumping into the fair trade game.

"It is great to have an environmental story behind the materials but if the product doesn't look and feel great, it wont sell"

Nicole Kaldes, Aveda

Global Mamas, a women's collective based in Ghana, showed off their batik print dresses during the runway show in a video produced by Tabeisa, a London-based investment group for artisans in developing countries with the slogan 'Exchange Designs, Change Lives'.

One example of its fair trade practices is a pact between Aveda, owned by the US cosmetics giant Estee Lauder, with aborigines in central Australia to guarantee them a good price on their sandalwood, used in health and beauty products.

Nicole Kaldes, Aveda's representative at the Paris show, said: "It is great to have an environmental story behind the materials but if the product doesn't look and feel great, it wont sell."

"And small companies may need investment by large groups to continue making products that look and feel great.”