Livia Firth rounded up fashion names including Tom Ford, Natalie Massenet, Nicole Farhi and Stephen Jones on Wednesday night for the London premiere of “The True Cost,” a hard-hitting documentary on the garment industry that she co-executive produced.

The film, directed by Andrew Morgan, screened in Cannes earlier this month, ahead of its global release Friday. Morgan was prompted to examine the industry following the Rana Plaza tragedy in Bangladesh in 2013, when a garment factory collapsed, killing 1,129 workers. In his film, Morgan trains his eye on the effect of the entire fast-fashion supply chain, from farmers in India being indebted to corporations selling genetically modified cotton, to pesticides used in cotton production causing birth defects in Indian children and workers’ wages being driven down as firms aim to reduce costs.

“We’ve all been entrapped in the last 15, 20 years by fast fashion, to buy so fast, at always the cheapest prices, and this movie shows what the real cost of this cycle is,” said Firth, who is known for launching the Green Carpet Challenge. As part of the initiative, she commissions designers to create sustainable creations, which she wears when she hits the red carpet with her actor husband Colin Firth.

After the screening, Firth acknowledged that “the fast fashion industry obviously won’t like this movie. It really pins down the damage that they are doing — unless fast-fashion brands pay their workers more, you can’t change anything,” she said. “You can produce beautiful organic cotton collections for window dressing, but you’re not actually trying to rectify the problem.” Instead, Firth urged fast-fashion businesses to “start counting human capital and natural capital in your business. If you don’t, in 10, 15 years’ time, you won’t have these resources,” she said.