Best known for co-founding the Green Carpet Challenge that has taken the fashion world by storm, Livia Firth has now designed her own pieces for new ethical fashion line Livia Firth Designs.

Firth is already creative director of eco-age.com, the shop within a shop on YOOX's shopping website Yooxygen, which aims to spread environmental awareness by collaborating with a series of international brands, designers and talents.

On the site, shoppers can purchase from a selection of clothes and accessories Firth praises for their style and eco-sustainability, via the collection Eco Age by Livia Firth.

Meanwhile, her new sustainable fashion line Livia Firth Designs will launch this September on YOOX, with items including a little black dress in organic wool with a vegetable tanned leather obi belt, two styles of woollen cloche hat and a hand-crafted butterfly necklace.

Since her actor husband Colin won a Golden Globe nomination for Tom Ford's A Single Man back in 2009, Firth has only worn dresses made from eco-friendly fabrics during the ceremony season, including one upcycled from an old Tom Ford suit.

The Italian-born former film producer famously convinced big-name creators such as Tom Ford, Chanel, Giorgio Armani, Gucci and Stella McCartney to sign up for the Green Carpet Challenge -- the initiative she founded in 2009 along with British journalist Lucy Siegle.

Other famous faces to have championed sustainable clothing include Harry Potter actress Emma Watson, who last year designed her third and final collection for ethical fashion label People Tree and supermodel Gisele Bündchen, who is currently promoting a T-shirt designed by Vivienne Westwood to support reforestation in Europe.