The Co-op is to become the first UK retailer to use only Fairtrade cocoa in its products, giving a huge boost to the Fairtrade movement.
More than 200 products will be included in the switch - including items as tiny as the sprinkles on its doughnuts to main ingredient products like chocolate cakes.
The company already sources products from over 20 countries and supports around 250,000 farmers.
The Co-op estimated that the move was worth over £7m to the industry and will generate £450,000 in the Fairtrade premium every year.
Other food retailers were urged to follow the lead by pledging their commitment to deal with Fairtrade cocoa farmers.
Brad Hill, Co-op's Fairtrade strategy manager, said: "The UK is the world's biggest Fairtrade market and the world's fourth biggest consumer of chocolate, but our manufacturers and retailers still only source a tiny amount on Fairtrade terms.
"When we consider that demand for cocoa is set to rise by 30% over the next three years alone, it's imperative that we keep moving forward with sustainability initiatives in order to shape this industry. We must help to improve the lives of farming communities who are still suffering a raw deal."
Michael Gidney, chief executive of the Fairtrade Foundation, commented: "Chocolate is often seen as an indulgence in the West, but for the millions of small-scale farmers who grow cocoa it can mean the difference between poverty and prosperity.
"We are very pleased to build on our long-standing partnership with the Co-op. As a leading retailer with strong ethical values, the Co-Op's commitment to Fairtrade is exemplary.
"After 20 years the Co-op remains one of Fairtrade's most important allies in helping farmers get a better deal and this move again sets the standard for other retailers to follow."
The announcement was made ahead of Fairtrade Fortnight, which starts on Monday.