Uk Labour government Business Secretary Lord Mandelson faced mounting pressure to establish a supermarket ombudsman amid a pledge by the Conservative Party to appoint a watchdog that would protect suppliers from abuse.
The anti-poverty charity War on Want called on Mandelson to act after shadow environment secretary Nick Herbert announced that a future Tory government would appoint a supermarket ombudsman.
Herbert will deliver the promise in a speech this week at the Oxford Farming conference.
The charity welcomes the pledge as a step towards a fair deal for overseas workers who supply British stores.
According to War on Want, many South Africans earn well below a living wage on farms supplying fruit and wine to British supermarkets.
The charity's research has also revealed that Kenyan and Colombian workers face poverty pay supplying flowers to UK supermarkets.
War on Want is demanding that a watchdog should extend beyond agriculture to all sectors, including clothes suppliers.
The charity has revealed workers making garments for Tesco and Asda in Bangladesh receive only half a living wage.
Simon McRae, senior campaigns officer at War on Want, said: "Supermarkets in the UK are shamelessly exploiting overseas workers who supply produce sold by their stores.
"While the government fails to do anything about the abuse of suppliers, even the Conservatives now recognise the need for action. The government must introduce a watchdog as an urgent priority."
Research by leading economist Roger Clarke found the ombudsman would not only protect suppliers.
It would also cost supermarkets just 0.005% of turnover, improve products, and, in some cases like agricultural products, lower prices.
And eight in 10 shoppers want a watchdog, according to a YouGov poll.
War on Want has led moves for a supermarket ombudsman with other groups, backed by more than 60,000 people who have taken action to strengthen the drive.