Fashion industry 'needs to be more transparent'
The fashion industry is one of the biggest polluters in the world and a major contributor of greenhouse gases.
Parts of the industry have also been accused of breaching human rights and not paying workers enough.
But the latest Fashion Transparency Index has revealed some brands are beginning to show signs of improvement.
Campaign group Fashion Revolution looked at 200 labels' social and environmental policies.
It found the most transparent brands were Adidas, Reebok and Patagonia - they each scored 64% of the total points possible - followed by Esprit and H&M.
"We know anecdotally, that there's a sense of competition between brands to do better than their competitors, particularly between sports or luxury brands," Carry Somers, founder of Fashion Revolution told Radio 1 Newsbeat.
"But we do really have a long way to go, the average score is only 21%."
In a statement on its website, H&M said: "We believe being transparent - clear and open - about how and where our products are made, is an important part of helping us become more sustainable.
"The more we share, the more we learn, and the more we can identify the areas to focus on."
While Fashion Revolution says it's good news that more brands are becoming more open by publishing their policies, it doesn't mean they're the most ethical or sustainable.
"What we need to see the brands doing is to disclose more about the outcomes of their polices and the tangible impacts they're having on the lives of their producers and environment," Carry Somers says.
"We have the right to know that the money we're spending with the brand isn't supporting human rights abuses and environmental degradation - transparency is the first step in making sure this takes place".
The Index also looked at fashion's environmental impact.
It found that more than half (55%) of the 200 brands are publishing their annual carbon footprint on the company's own sites, but only 19.5% reveal carbon emissions in the supply chain - which is where more than half of the industry's emissions occur.
The Fashion Transparency Index started after the Rana Plaza factory collapsed in Bangladesh in 2013.
More than 1,100 garment workers died and hundreds more were injured.
The disaster exposed poor safety standards and regulation, and raised questions over the responsibilities of the big retail brands given their push to keep prices as low as possible in an era of fast fashion.
'Fashion brands need to do better'
Not all brands are telling the public about their human rights and environmental policies, practices and impacts - five scored zero on the Index.
They included Eli Tahari, Jessica Simpson, Mexx, Tom Ford and Chinese menswear brand Youngor.
Another 10 brands revealed almost nothing (less than 2%), including Longchamp, Max Mara and New Yorker.
"There are still far too many big brands lagging behind," Fashion Revolution policy director and report author Sarah Ditty says.
"Major brands are disclosing very little information and data about their purchasing practices, which means that we still don't have visibility into what brands are doing to be responsible business partners to their suppliers."