Foreign workers 'earn 7p an hour'
The anti-poverty charity War on Want said Primark was ignoring the rise in basic living costs in the Bangladeshi capital Dhaka, leaving workers worse off than they were two years ago.
It is calling on the British Government to introduce regulations to ensure a living wage for overseas suppliers and allow staff claiming exploitation to pursue claims through UK courts.
The charity said high inflation and increasing fuel costs in Bangladesh led to a 70% increase in the price of low-quality rice. The cost of other cooking items including oil, onions, pulses, wheat and flour had soared by 30% to 60%.
Workers claimed they needed the equivalent of £44.82 a month to feed their families and pay for clean water, shelter, clothes, education, health care and transport.
War on Want said the average worker earned £19.16 a month, with the majority living in small, crowded shacks, many lacking plumbing and adequate washing facilities.
The report also claims workers making clothes for Asda and Tesco are paid similar amounts.
War on Want campaigns and policy director Ruth Tanner said: "Primark, Asda and Tesco promise a living wage for their garment makers. But workers are actually worse off than when we exposed their exploitation two years ago. The UK Government must bring in effective regulation to stop British companies profiting from abuse."
All three retailers denied the allegations, saying they were committed to the ethical treatment of suppliers.