The Fairtrade Foundation said many cocoa farmers in West Africa, where 60% of cocoa is grown, are living in poverty and unable to pay for essentials such food, medicine or schooling for their children despite the chocolate industry being worth £4 billion in the UK.
In a report to launch Fairtrade Fortnight, the organisation says farmers could live a decent life for £1.86 a day, the average price of a large bar of chocolate, and argues that living incomes are key to ensuring the future sustainability of cocoa.
It said women cocoa farmers had fewer rights than men and rarely owned land, therefore receiving even less of the profits, but worked in the fields and did the "lion's share" of labour involved in bringing crops to market.
Fairtrade is raising the price it pays for cocoa by 20% in October.
But it said just 6% of cocoa globally was Fairtrade-certified and is calling for collective action from the Government, industry and consumers.
The Fairtrade Foundation is calling on the government to join the German government's Living Income Task Force, make living incomes a priority for UK aid and incorporate living income into Government Business and Human Rights policies.
It is also urging chocolate companies, traders and supermarkets to commit to sourcing their cocoa on Fairtrade terms as a first step and committing to ensuring that cocoa farmers receive a living income by 2030.
Dr John Sentamu, Archbishop of York and Fairtrade patron, writes in the report's foreword: "Shameful as it is inexcusable, exploitation and poverty continue to hide under the seductive packaging of our favourite chocolate.
"All of us have a moral responsibility to act. We all, global citizens, businesses, governments, must do more."
Fairtrade Foundation chief executive Michael Gidney said: "As a nation of chocolate lovers, it is shocking that the women who grow and harvest the cocoa that goes into our treats are barely able to put food on the table nor send their kids to school, the majority of us think the exploitation they suffer is unacceptable.
"Everyone is entitled to a decent income, it is a human right. As a country we've signed up to end poverty by 2030, but that won't happen unless people earn more for the work they do, so we're calling on governments, businesses and the public to pledge to make living incomes a reality.
"Whatever happens with Brexit, our leaders must make sure trade deals put poverty reduction first. If that matters to you please sign our petition."
Meanwhile, Waitrose & Partners has committed to making all cocoa in its own brand confectionery 100% Fairtrade by the end of the year.
Lizzie Sutcliffe, buyer of confectionery at Waitrose & Partners, said: "Responsible sourcing is something both we and our customers care deeply about.
Given the popularity of our own brand confectionery and Fairtrade products in store, our new cocoa commitment is a natural fit and the perfect act of solidarity to support the Fairtrade Foundation in their campaign.
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