Two years later, out of a 'desire to hear from their perspectives', Harney, a resident of Hong Kong, decided to write a book about migrant workers, their bosses and the eco-system they live in.

Based on a year's research in a swathe of mostly southern mainland cities, The China Price: The True Cost of Chinese Competitive Advantage brings us face to face with the varied lives inside these factories. Meet Li Gang, a low-ranking employee in a plastic bag factory who worked 18 hours a day, seven days a week, for a meagre salary until he lost a limb to a machine; Tang Manzhen, the widow of a jewellery factory worker who died from silicosis, an incurable lung disease contracted from grinding semi-precious stones; and Li Luyuan, a worker at a cashmere-goods factory who sleeps in a crowded room with 11 other girls while nursing a dream of a more civilised life.

In one way or another they all pay a big personal price to sharpen the mainland's competitive edge, paving the way for it to sell inexpensive consumer goods to the US and beyond.

The trade conflicts between Beijing and the west result in a 'total disconnection' between the two worlds, Harney says. Through her portraits, she has sought to give a human face to the mainland's industrial machine and demonstrate how 'our shopping habits in the west have real impact on lives in other parts of the world'. Harney, who until 2005 was the Financial Times' south China correspondent, left the paper to become a research fellow at the University of Hong Kong so she could focus on writing the book. Being a tall Caucasian foreign correspondent with long brown hair and blue eyes has been a mixed blessing for her when trying to report unobtrusively.

Her appearance became an impediment, for instance, when investigating the widespread 'shadow factory' system, wherein mainland suppliers would build a model factory to solicit western contracts while concealing illegal practices in shoddy factories with questionable methods that produce most of the goods. Harney says she was never able to sneak inside to view shadow operations because she clearly 'didn't belong there' and she feared going undercover as a factory worker could expose her sources.

At other times her status as a westerner helped because she represented someone outside the system in whom subjects felt comfortable confiding. So the upwardly mobile owner of an illegal private mine took her on a personal guided tour of his hidden unlicensed pits in the remote mountains of northern Shanxi province, while the owner of an illegal factory showed Harney how he cooked the books and cut corners on the quality of materials and working conditions to deliver goods abroad quickly at rock-bottom prices.

While the shadow factory system is fuelled by western investment, there are many willing partners. Migrant workers want more hours so they can earn more money to send home. And foreign buyers demand the cheapest prices to undercut competitors while looking the other way when it comes to dishonest practices.

But Harney also sees evidence of change. Workers are increasingly aware of their labour rights, especially those born in the 1980s under the one-child policy who are starting to challenge factory bosses. Their understanding of their basic rights is increasingly sophisticated and prompts demands for more rest, better pay and improved working environments.

Rising land prices and regional labour shortages are also forcing many factories to move into higher-value industries where the labour component accounts for a smaller percentage of total costs, or to go to less expensive areas inland with implications for the global supply system. 'When workers are living closer to home they are unwilling to work long hours at weekends,' Harney says. 'They'd rather see their families.'

Writing this book has made Harney more aware of the connection between the choices western consumers make and the conditions faced in the producing countries. 'By expecting ever lower prices, we are in a sense fuelling this system that creates pollution and poor working conditions in China.' Western consumers shouldn't expect the mainland to clean up the environment and adopt model labour conditions, she says, without being willing to pay higher prices.

For Harney, one of the high points in writing the book was making the acquaintance of factory girls in Shenzhen, where she was based for 10 months. 'They were some of the most inspiring people I had ever met, full of energy and life and hope, even after a long day on the assembly line,' she says.

It was while sharing meals in the women's dormitories, walking with people to work and sitting in parks together on their days off that she formed meaningful friendships - and became 'one of the girls'.

The China Price by Alexandra Harney (Penguin Press, HK$208)