"The world of celebrity leads by example and generates an aspirational desire for branded products. These stars have the responsibility to make sure that the brands they are endorsing are not damaging the planet."
Celebrities such as Sienna Miller are being urged to sever their ties with luxury brands whose allegedly poor environmental practices are highlighted in a damning report today.
Some of the most exclusive companies in the world of fashion and jewellery are heavily criticised in a study for WWF which ranks them based on the sustainability and ethics of their business.
Bottom of the list was the Italian leather company Tod's, endorsed by Miss Miller, which scored 35 out of 100 and was awarded a grade F. L'Oreal, associated with Claudia Schiffer and Penelope Cruz, came top with 70 and earned a grade C+, just ahead of Hermes.
The report, Deeper Luxury, says "the power of these celebrities to build brand value is enormous".
It adds: "Tod's first celebrity ambassador, actress Sienna Miller, campaigns against climate change through her association with Global Cool. She also endorses Tod's, which came bottom of our index of environmental, social and governance perfomance."
The study looks at the top ten holding companies for luxury brands including Gucci, Yves Saint Laurent, IWC, Garnier and Louis Vuitton. The ranking system is derived from their own sustainability reporting, as well as the way they have been judged in the media and by non-governmental organisations.
Researchers found that in some cases the luxury goods industry, worth £77 billion worldwide, is depleting natural resources, exploiting labour and hiding its supply chain from outside scrutiny.
Conflict diamonds - mined and sold in warzones to fund military campaigns - are being used in some luxury items, while gold mining is displacing communities, contaminating drinking water and destroying pristine environments.
In July the luxury cosmetics firm Garnier, a subsidiary of L'Oréal, was found guilty of racial discrimination after it sought to exclude non-white women from promoting its shampoo in French stores.
The report noted that LVMH, owners of Louis Vuitton and TAG Heuer, was de-listed from the FTSE4Good index earlier this year as a result of poor compliance with supply chain requirements.
The US firms Coach and Tiffany scored badly on environmental factors, due to a lack of reported environmental monitoring or performance. An unwillingness to respond to questionnaires resulted in Tod's coming last, just behind Bulgari and Richemont - owner of Cartier and IWC.
Anthony Kleanthous, WWF's senior policy adviser, said: "This report is a call to action for the world's top brands to improve the way they do business. Luxury companies must do more to justify their value in an increasingly resource-constrained and unequal world.
He said that many celebrities now shunned conflict diamonds as a result of the film Blood Diamonds and called for them to take the same attitude with other luxury goods. The wildlife charity is urging famous names to adopt their "star charter" - a commitment to consider the environmental and social performance of the brands that they endorse.
"The world of celebrity leads by example and generates an aspirational desire for branded products. These stars have the responsibility to make sure that the brands they are endorsing are not damaging the planet. Let's face it, who wants to pay extra for a dirty brand?" said Mr Kleanthous.
A spokesman for Tod's said: "Tod's is committed to the process of developing long term strategies to address the very serious issues of global warming, ethical production and the potential environmental crisis.
"Tod's products are made in Italy, skins sourced from Europe and the USA only and from the late 1980's Tod's has been using natural vegetal treatments on skins over the chemical equivalent, where possible, and is actively endeavouring to increase all aspects of sustainable brand development.
"We understand that the contents of this report are based on lack of information in the public domain or EIRIS as opposed to fact."