London (CNN) -- The red carpet is fashion's grandest stage where stars line up to see and be seen. But who you are wearing is as important as who you are.
If Livia Firth, wife of Academy Award-winning actor Colin, gets her way, the kind of fabric you are wearing will be just as essential.
Now in its third year, the Green Carpet Challenge was established to persuade top designers to dress the world's most famous faces in clothing that is ecologically friendly and socially responsible.
"First of all, you want to wear something that is made with non-toxic materials and dyes and also that it's made by people who are happy fundamentally," Firth says.
She has worn yarn made from recycled plastic bottles to the Golden Globes, material from repurposed thrift store finds for the Oscars and discarded fabric to meet Queen Elizabeth II.
Now she is persuading some of the biggest names in film and fashion to follow suit including designer and film director Tom Ford, Hollywood legend Meryl Streep and rising star Michael Fassbender.
"A designer will create a gown for an actress anyway. So what we do is to work with the designers to switch the fabric to eco-alternatives," Firth said.
One of Firth's own "green carpet" triumphs was an emerald green gown made of upcycled fabric created from scratch by British designer Henrietta Ludgate who produces her designs out of a small workshop/showroom in London.
"We source from mills in Scotland and England. We upcycle fabrics and we produce everything locally. It's zero clothes miles," Ludgate said.
Sourcing fabrics this way allows Ludgate to oversee every step of the production process which she says leads to a superior product but not perhaps superior profits.
"People buy for design rather than sustainability. When they find out about it, I'm hoping that they will buy more!"
But fashion journalist Lucy Siegle would like to see people buying less.
She started the Green Carpet Challenge with Firth in 2009 in the hope it would encourage people to try new things with uncommon materials and clothes already in existence.
"Innovation, as it's told by mainstream fashion, is about wearing the latest look from the latest celebrity or whatever," Siegle said.
"Ironically, we are working with celebrities, but we're showing that it's not just about imitating a trend. It's actually about techniques, about tailoring and heritage fabrics. It's about the narrative of a piece," she added.
It's a trend that Livia Firth hopes will continue.
"Next year we hope to have a dedicated lane at the Oscars for the Green Carpet Challenge people," Firth said.