Primark's market share has increased despite the credit crunch.
Panorama puts Primark's claims that it can deliver cheap, fast fashion without breaking ethical guidelines to the test.
Posing as industry buyers in India, the programme's reporter Tom Heap and his team find some of India's poorest people working long, gruelling hours on Primark clothes in slum workshops and refugee camps.
These were far away from the Primark approved and inspected factories; breaking promises on child labour, working hours and wages.
When presented with the results of the investigation Primark sacked three suppliers and announced it was setting up a children's foundation.
Panorama: Primark on the Rack can be seen on BBC One at 9pm on Monday 23 June.
Update June 2011: The
BBC Trust has upheld a complaint
from Primark about this programme.