THEY had 40 bags between them. Jean Barbour and Jacqueline Cormack were yesterday heaving pyjamas, tops, jeans, slippers and box after box of decorations down Glasgow's Sauchiehall Street. And all from Primark, the Irish-owned low-cost store.

"It's just brilliant value for money, " explained Mrs Cormack, who had come over from Edinburgh just to do her Christmas shopping at Primark. But she wasn't so sure of the value when she heard why the shop is so cheap.

"They pay 5p an hour?" she asked, learning of an investigation published this week by charity War on Want into the Bangladeshi factories that supply the Irish low-cost store and its supermarket rivals, Asda and Tesco.

"I wouldn't mind paying a bit extra, " Mrs Cormack said. "I got jeans for GBP4 today. They could have paid their workers a bit more and still given me a very reasonable price."

The investigation, which was first reported in The Herald yesterday, doesn't make easy reading for anyone tempted by the bargains in any of the stores.

Researchers working for the charity talked to employees at six factories in Bangladesh which work on orders from the three UK retailers.

Some were paid just GBP8 a month. The lucky ones, investigators found, earned GBP16 operating sewing machines. That is nothing like enough to live on, locals said. Even in poverty-stricken Bangladesh.

"The wages I get are not enough to cover the cost of food, house rent and medicine, " said Mohua, a worker in a factory making clothes for Tesco and Asda's George range. Her friend Humayan, who works in the same business, said she couldn't make ends meet. "With my earnings, " she said, "it is difficult to meet living costs." Both are on GBP16 a month, the equivalent of 5p an hour for 80-hour weeks.

Almost all the workers were female. Many were just girls, children. Some, locked in and not even allowed to use the toilet, were sexually harassed by their managers and cheated out of overtime payments.

Earlier this year a spate of fires left more than 100 dead. Conditions, already costing lives, are getting worse. Wages, in real terms, halved in the 1990s in Bangladesh, making the country's labour the cheapest in the world.

The reason? War on Want pins at least part of the blame on the growing demand for chic on the cheap.

The charity, in its report, said: "While poor government policy and the attitude of factory owners is an important part of the story, the price-cutting tactics of lowcost clothing retailers sourcing from Bangladesh have been the driving force."

Primark, Asda and Tesco stress they rigorously vet their suppliers in Bangladesh and elsewhere. Asda even called it "chic with a clear conscience".

The firms inspect factories, they say, and work to ensure employers respect trade union rights. That would have come as news to the workers who talked to War on Want.

Abdul, who makes garments for Asda and Tesco, put it bluntly: "If anybody tries to form a union he will be dismissed from his job."

War on Want chief executive Louise Richards said: "Bargain retailers such as Primark, Asda and Tesco are only able to sell at rock bottom prices in the UK because women workers in Bangladesh are being exploited.

"The companies are not even living up to their own commitments towards their overseas suppliers."

SO, is there a problem with the inspection regimes the big retailers operate? Yesterday they said they would like War on Want, which declined to name the factories it investigated, to name names.

All three firms said they were determined to provide cheap clothes, not least for Britain's poorest families, but did not want to do so at the expense of poor in the Third World.

Asda hinted it was not just the bargain basement firms that used low-cost labour. The company said it used the same factories as big designer labels.

However, the three firms are now so cheap they are giving charity shops a run for their money. Mrs Barbour and Mrs Cormack, for example, were paying less for their presents for their families in Primark than they would have done at a nearby Oxfam shop. Jeans at George start at GBP3. The company is advertising menswear for GBP2.50. There are children's T-shirts going in some stores at GBP1.50.

The shops, of course, don't just depend on cheap labour for their success. All three have a remarkable success turning around catwalk and celebrity fashion trends at lightening speed.

No sooner have shoppers seen photographs of a celebrity wearing a designer dress on the red carpet, than a replica of the same outfit is hanging on the rails at bargain prices. Few buyers worry that it may have been sewn up by a 13-year-old Benghali girl.

Recently Primark sold a gold sequin mini dress, reminiscent of an Yves Saint Laurent dress, for less than GBP30.

Elizabeth McMeekin, The Herald's fashion writer, said: "At this price shoppers can buy an outfit, wear it once or twice safe in the knowledge that they haven't spent a fortune and are right on trend for the season.

"It doesn't matter that the same dress won't be in fashion next spring. This is the fast food market of the shopping world, as it were."

Student Siobhan McGill has an e-mail pen pal in Bangladesh and is clued up on the realities of life there. But she still shopped at Primark yesterday, picking up a Christmas gift at half the price it would have cost in a designer store. "I am happy to pay more, " she said. "But we shouldn't boycott the shops.

"Then the people will just end up on the streets. We just have to make sure they treat their workers more fairly."

So what happens to all the clothes we buy on the cheap? A lot, sometimes barely worn, end up in landfill as last year's fashion. War on Want called its report Fashion Victims. Scottish shoppers might not be paying the price - but someone is.

TESCO

Sales in 2005: GBP41.8bn

Profits in 2005: GBP2.21bn

Employees: 389,000

Tesco says it pays more than the Bangladeshi minimum wage.

A spokesman said: "Tesco offers affordable clothing to UK customers, including many low-income families, but this is not achieved through poor working conditions in our suppliers' factories.

"All suppliers to Tesco must demonstrate that they meet our ethical standards on worker welfare, which are closely monitored."

PRIMARK

Sales in 2005: GBP1.3bn

Profits in 2005: GBP185m

Employees: 18,000

Primark attributed the chain's low prices to good technology, efficient distribution and supply, bulk buying and minimal advertising spend.

"We are fully committed to the campaign to improve working standards in Bangladesh, " a spokesman said. "If War on Want will give us details of which factories are ignoring the code we will investigate. If the allegations are true, we will demand immediate change."

ASDA

Sales in 2005: GBP14.9bn

Employees: 134,000

Asda said it shared factories in Bangladesh with some of the world's biggest designer labels and carried out 13,000 factory audits to ensure workers were not exploited.

"We want to work closely with the Bangladesh government to ensure that they take our standards as seriously as we do, " a spokesman said. "We are currently trying to arrange a meeting with [War on Want]."

Asda is owned by WalMart, whose UK subsidiary made GBP571m in 2005.