Take, for example, a striped button-down shirt you may have bought in a Bali boutique. It could well have been imported to the store from the brand headquarters in Italy, perhaps via a Las Vegas showroom, but it could have been produced in Guangdong, Turkey or Bangladesh, with cotton farmed in Brazil. Finally, it is worn in Hong Kong.

The process involves various companies with differing policies in a number of countries; it is a journey undertaken by most fashion garments today. The process is unwieldy and the carbon footprint, inflated by all that travel, is large. Almost insatiable consumer demand and the mass production employed to try to satisfy it exacerbate problems such as competition for arable land, pollution and the exploitation of labour.

Nevertheless, one of the world's most successful high-street fashion companies is out to prove that a degree of sustainability and a high-turnover retail model can go hand in hand.

Hennes & Mauritz (H&M) started out as a womenswear store and was established by Erling Persson in 1947 in Vasteras, Sweden. Today it has about 116,000 employees and 3,300 stores globally, the Hong Kong outlet that opened in 2007 being Asia's first.

H&M and companies such as Zara, Target, Topshop and Forever 21 bank on a fashion-forward, fast-trend model, wherein people buy up-to-date stylish gear at affordable prices every few weeks. Although this model has democratised fashion and style, it results in a vast amount of textile waste - in production and as a result of clothes being quickly discarded - energy consumption and environmental pollution.

"Sustainability is integrated in our business," claims Leyla Ertur, H&M's manager of production for China, Myanmar, Vietnam and Cambodia, when we meet in Guangzhou, prior to a visit to one of the brand's supplier factories. "Rather than having a separate sustainability department, whatever we do [whether retail, logistics or purchasing], it's part of the business."

Ten days ago, the brand launched a family denim line that uses 58 per cent less energy and 56 per cent less water than are required for the brand's main denim products, as well as a greater amount of recycled and organic fibres.

The company is the world's No1 user of certified organic cotton (using 29 per cent more last year than in 2012) and, with the help of red-carpet appearances on Hollywood celebrities, its widely publicised Conscious Collection - featuring pieces such as a 100 per cent organic cotton top, a floaty 100 per cent organic lace bohemian dress and a flamenco dress made using 100 per cent recycled polyester crêpe - has become popular.

In 2003, H&M became the first fashion label to launch garment collection hubs in stores worldwide. The chain recycles the material (as more clothes or for car insulation, for example) or sells the clothes on as second hand, but a "10 per cent discount off your next purchase" incentive to hand over old garments was criticised for encouraging spending.

Other contradictions inherent in a company using a fast-fashion model while extolling the merits of eco fashion have not gone unnoticed.

"It's very hard to be sustainable, shifting these kinds of volumes, with the poor quality of garments [associated with fast fashion]," says Diana Verde Nieto, chief executive and founder of the Positive Luxury assessment service. Her membership programme awards the Butterfly Mark to, according to the website, "luxury brands that are taking positive steps to better society and the environment".

"Sustainability is not just good social and environmental standards, but considering the entire life cycle of the product, from sourcing to manufacturing and disposal.

"For a product to be sustainable, durability is an essential quality," says Nieto, explaining why she prefers the longer-lasting, quality products associated with "luxury", although that doesn't necessarily mean expensive designer brands.

"Sustainability and luxury is not an oxymoron but two sides of the same coin - luxury is inherently sustainable and durable, with quality and craftsmanship."

Several high-profile designers have been vocal supporters of eco fashion. Stella McCartney is an avid advocate and practitioner. While refusing to use animal skins, she sources recycled, natural and renewable materials, makes biodegradable parts and never tests on animals.

Long-time environmental activist Vivienne Westwood this season launched a unisex vegetable dye collection through her high-fashion label. Liquorice root is used in the dyeing process instead of harmful chemicals and pieces are designed to be worn for years and passed between friends. Her mantra of "Buy less, choose well and make it last" is one that many eco-minded luxury labels claim to support.

"Be inventive with your wardrobe," Westwood said, when the collection was released. "Mix it up, substitute evening for day and vice versa … take beautiful pieces from your wardrobe or from that of your friend or partner and style together with your old favourites."

Unfortunately, McCartney and Westwood are in a minority and their output tends to be expensive. It is therefore crucial that market-dominating fast-fashion labels, with their massive clout, embrace practices that edge them closer to sustainability if any significant change is to be made.

"I think the biggest need in this sector is for more businesses to capitalise on sustainability as a moneymaker," says Christina Dean, founder of Hong Kong-based NGO Redress and the EcoChic Design Awards, which encourage sustainable practices among customers, designers and retailers. "If we can demonstrate that companies' bottom lines can be fattened up through, for example, less waste generated and greater natural resource efficiency, then we're onto a winner."

The ubiquity of H&M is testament to its popularity, but also a frightening reminder for some environmental activists of how rapidly fast fashion has taken over the retail landscape.

"Fast fashion … has never existed on this scale," says Nieto. "Even 10 years ago [it was still relatively undeveloped]."

Although the brand has made headlines for collaborations with some of the most respected fashion houses, including Karl Lagerfeld, Comme des Garçons and Stella McCartney, the bulk of H&M's business is based on a "buy often and cheaply" model. With H&M's rate of expansion - especially in the mainland, where the brand operates 200 stores - and the additional volumes needed to fuel that expansion, it is only natural for critics to argue that true sustainability would require a shift in business model.

Nevertheless, says Julia Bakutis, H&M's sustainability manager for the China region, "We want to run in a way that is economically, environmentally and socially sustainable". Perhaps with new sister labels such as & Other Stories and Cos, which focus on quality, timeless pieces aimed at an older clientele willing to spend a little more, the group is making progress.

One way mass brands improve standards in the manufacturing process is by rewarding production partners that implement greener technologies on their own initiative with extra business. One such partner for H&M is Yida Apparel, wholly owned by Hong Kong's Crystal Apparel, which has production sites in the mainland and elsewhere in the Asia-Pacific region.

The Yida denim factory we visit in Zhongshan counts the likes of H&M, Gap, Levi's, Wrangler and Target as clients.

Awards for enterprise and green entrepreneurship line the walls of the reception area.

Behind the reception, the large complex is separated into sections, each dealing with a different stage of production; the factory has more than 3,500 workers, from the white-coated technicians in the temperature-controlled research and development labs to the staff sewing at individual, ergonomically designed workstations.

The factory, which is criss-crossed by thoroughfares with names such as Innovative Road, Integrity Road Central and Energy Protection Road, does not feel crowded and appears well organised. Solar energy panels are plastered across outdoor surfaces.

Chiu shows us around each section, explaining its purpose while outlining the basic health and safety practices of the factory. Posters explain how salary structures are calculated, instruct on work safety and give notice about after-hours activities. Machinery provides a constant background hum.

As the tour progresses, pointed out are the decentralised air-conditioning systems, custom-designed lighting and air-drying facilities, all of which reduce energy consumption, and the recycling and filtration system for water reuse. Most of the pungent, indigo-stained liquid stored in large tanks at the back of the complex will be transformed into clear reusable water.

Investment in technologies such as ozone machines that use 90 per cent less water to achieve certain denim washes has given the factory an edge when it comes to satisfying customers demanding greener work practices. Transparency (apart from in the technology development labs) seems to be high - at least high enough to satisfy the brand representatives who make surprise inspections.

"The working conditions are pretty good, which is why I came back after leaving to have my child," says Chen Jinlong, from Hubei province, who has worked her way up to become a team leader, "and the salary is also quite high compared with other factories around here.

"There are classes for self development, a library and computers, too; that's why I've stayed."

As workers' rights NGOs in the region will tell you, most garment factories in the mainland have a long way to go before being able to boast of self- and career-development classes, counsellors, creches, basketball tournaments and other worker benefits that seem to be available at the Yida plant. But those that do will be rewarded with big orders and long-term contracts with H&M, says Ertur.

Big fashion brands can create massive positive (or negative) change across a region. H&M sources 80 per cent of its products from Asia and the standards it sets could trigger long-term shifts in producer countries.

"We directly employ over 110,000 people but, if you look at our supply chain, we impact millions, all the way back to the farmers who supply our cotton," says Bakutis. "We have a huge footprint and great responsibility."

Furthermore, like-minded fashion companies have begun to band together to bring more pressure to bear on certain aspects of the production process.

"A great example is the Sustainable Apparel Coalition, which is a group of brands working together to improve factory working conditions," says Bakutis. In January, British luxury brand Burberry announced it would join a list of 18 companies committed to eliminating the use of hazardous chemicals in their supply chains by 2020.

Such clout, though, exists only because of a large customer base. Aggressive expansion might be good for business and profits but, as Dean says, "The elephant in the room is our growing levels of overconsumption and, in turn, production.

"Because of this, competition for farm land and natural resources is getting more tense. At some stage, people will need to decide whether to eat food or wear fashion. Fashion designers and [others in the] industry who are smart enough to foresee this can create innovative business and design models based on reducing waste and sourcing waste textiles so as to decouple their business practices from virgin resources."

In the mainland alone, at least 20 million tonnes of textile waste is produced annually and, in 2011, Hong Kong sent 79,000 tonnes to its landfills.

Nieto, who started her organisation after founding a sustainability consultancy called Clownfish, says that, for her, "success is … to normalise sustainability".

The work of Clownfish "led to the opportunity of a lifetime: being trained by Al Gore at the Alliance For Climate Protection in Mexico," says Nieto. "He was launching his 2006 global-warming documentary ; he stood up for the importance of sustainability when no one else cared. He had such a dry sense of humour, and wore cowboy boots under his suit."

When she started Positive Luxury in 2011, "eco-" and "sustainable fashion" were not yet part of a serious global dialogue: "I wanted to unlock the potential brand value of sustainability and create a platform that allowed consumers to make informed decisions about the brands they were buying."

Nieto's Butterfly Mark is awarded to companies that apply to join her list and that eschew animal cruelty; act against sweatshops; care for the planet; and try to con-serve it. Their credentials are analysed by algorithms and Positive Luxury is backed by an advisory board that includes respected environmentalist Jonathon Porritt. Making the cut are mostly high-end labels such as Burberry, Céline, Alexander McQueen, Balenciaga and luxury watch brand IWC Schaffhausen.

The purpose of the mark is to "update consumers on a company's best practices and in turn keep those companies up to date with their consumers' views - from what makes a brand trustworthy to enhancing consumer experience".

H&M, however, is not on the list.

"They are making the right noises but I would not call them sustainable," says Nieto. "H&M is being compliant. There is no innovation in their business model."

She believes the product cycle needs to be slower and each item should last longer, and labels should go back to releasing "four to six collections maximum a year and explore business models such as customisation, tailoring".

Behind the scenes, many luxury brands are no better than mass labels in their sustainable or ethical codes, says Bakutis: "We share factories with a whole range of the fashion world, so I think this idea that fast fashion is separate is really not true."

Whatever their profile, though, "leaders of major corporations worldwide are increasingly realising that sustainability is an essential ingredient for a company's long-term success", says Neito. "Companies are recognising that business as usual is no longer an option."

Mass-market retailer Esprit, for example, recently launched the Recycled Collection, which uses the brand's own textile waste to create garments that are then sold at its normal price point.

informed and demanding than ever and commentators in the ethical-fashion industry say that interest and serious investment are growing fast. However, fast-fashion models continue to dominate.

"There is no point in us preaching more sustainable fashion design if the mainstream fashion market doesn't sit up, listen and then produce more sustainable fashion lines for consumers to buy," says Dean.

"There is a complex contradiction that shadows the mainstream fashion industry's sustainability efforts. While their sheer presence continues to push consumption, which is ultimately at the root of fashion's woes … they are innovating within their supply chains and driving better product lines to market."