The designer shopping bag aimed at promoting green awareness was made using cheap labour in China, according to an Evening Standard investigation.

The “I’m not a plastic bag” bag became a must-have fashion item even before 20,000 of them sold out within an hour at Sainsbury’s. Women queued from 3am to get one of the Pounds 5 cotton bags made by designer Anya Hindmarch they are now changing hands on eBay for Pounds 225.

At the first sales of the bag, Hindmarch said: “The idea was to create something that was really desirable to highlight ethical issues.” Today Sainsbury’s was accused of hypocrisy after it admitted the bag was made in China and was neither organic nor fair trade. The chairman of an influential Commons committee said Sainsbury’s had “tarnished” its image as a promoter of fair trade products.

A campaign group highlighting the exploitation of workers in the fashion industry said making the bag in China dented the bag’s ethical claims.

The fact the bags have been sent thousands of miles from Asia raised questions about whether its carbon footprint is threatening to offset its environmental benefits.

A spokeswoman for the designer admitted the bag, billed as “making a difference to the world”, was “not perfect”. A Sainsbury’s spokeswoman said: “While the bag is made in China it is not manufactured with ‘cheap’ labour nor does it exploit local workers.” The spokeswoman did not name the factory, but claimed: “The factory pays

double the Chinese minimum wage for that province. The factory also complies with all aspects of Chinese labour law andworks with an international human rights consultant who advises to review its operations.” However, Martin Hearson, of pressure group Let’s Clean Up Fashion, said: “This is bordering on the hypocritical..

There is an incompatibility in claiming a product is ethical and manufacturing it in China.” According to the Fairtrade website, no cotton produced or manufactured in China is sanctioned for sale as fair trade.

Malcolm Bruce, chairman of the international development select committee, said: “This tarnishes Sainsbury’s image as a company that supports fair trade.

It should have made a positive attempt to ensure this does not come from potentially exploited sources.” Mr Hearson claimed workers in China’s garment industry typically are paid 20p to 30p an hour. He also said cotton which is not fair trade is often picked by child labour.

The “I’m not a plastic bag” comes with a blue tag which explains the bag offers an alternative to plastic bags which “have a negative impact on the environment”. No profit is made from the sale of the bag.

The Sainsbury’s spokeswoman added that because the bag was a branded product, made by Hindmarch, “we’re not at liberty to disclose details on the supplier”. She also said: “I can confirm it [the factory] has been visited to ensure high standards of ethical trading.” A spokeswoman for Anya Hindmarch said the company made no secret that the bag was made in China, adding: “We never claimed this bag is perfect.

We just tried to use our influence as a maker of luxury goods to make it fashionable not to use plastic bags.”