Despite the factory collapse in Bangladesh, ethics are soon forgotten when faced with a £5 dress

The fashion equivalent of fast food, Primark has created a new breed of shopper: who considers its discount clothing so addictively cheap and disposable that they hoard items with little concern if they need or want it.

At Primark's flagship branch in Oxford Street, central London, Hannah Rose, 21, is shopping with her friend, Jordan Mogford, for a trip to the US with Camp America.

Hannah admits she doesn't bother taking clothes back to the store if she doesn't like them after she gets them home. "If it's only £2 there's no point, I'll just shove it to the back of my wardrobe," she says. "The clothes last a couple of months and then break and you have to go and buy more... I bought these shoes for our trip because they'll get ruined, but it doesn't matter."

"It's like a jungle," agrees Jordan, 18. "I don't try anything on, it's just too busy." However, she at least says she will "try it on at home and take it back if I don't like it".

While Primark has become increasingly popular for its prices, many customers know its range of T-shirts, shoes, skirts and jeans are inexpensive largely thanks to the low cost of sourcing them in less-developed countries.

Primark bosses said they were "shocked and saddened" by the collapse of the factory in Bangladesh, after confirming that one of its suppliers occupied the second floor of the eight-storey building. The company has been dogged by rumours that it uses child labour since 2008, when it axed three suppliers in India for passing work to unapproved sub-contractors who used under-age workers. It has also confirmed that it does not use child labour now.

But what effect this has upon shoppers, even those who have been suspicious of the ethics surrounding cheap clothes, is minimal when they are faced with a £5 dress. Primark's parent company said like-for-like sales rose by seven per cent in the 24 weeks to the start of March, a performance it described as "exceptionally strong".

"I've heard a lot of rumours about [Primark using child labour] so I wouldn't be surprised. It is so cheap, they must do," says Hannah, but she still buys the clothes.

"Every shop is the same," says Melanie Pogoda, 28, a tourist from Switzerland. "If you want quality stuff you have to go to a fair-trade shop and they don't sell the things I want to wear."

Traditionally, Primark shoppers buy in bulk, leaving the shop laden with clothes, shoes and accessories. The brand, dubbed "Primani" by its fans, doesn't have a website as it believes its low-cost, high-volume business model wouldn't be an attraction online. But competition on the high street means more shops are driving their costs down by using factories in developing countries to make cheap clothes quickly.

Primark claims it can take as little as six weeks for catwalk styles to appear in shops – and this doesn't just attract teenagers. "It's cheap and there's a lot of variety for young people," says Claire O'Brien, 53. "I think it should be investigated. They were paying [the Bangladeshi workers] their wages but it doesn't necessarily mean Primark were negligent."

Rabih Galach, 35, a banker, says Primark is good value for money. "We have disasters all over the world every day. I'm from Lebanon and I hear about Palestine and Syria every day. I can sympathise, but it won't stop me buying from there."