COCOA grown illegally in a protected Nigerian rainforest is beong sold to companies supplying major chocolate-makers such as Mars and Ferrero, an investigation has revealed.

The Associated Press (AP) news agency documented farmers harvesting cocoa beans in the conservation areas of Omo Forest Reserve, which is home to critically endangered African elephants, pangolins and white-throated monkeys.

Cocoa from the region is purchased by some of the world’s largest cocoa traders, according to company and trade documents and AP interviews.

These are then sold to companies making chocolate products including Snickers, M&Ms, Twix and Nutella.

Government officials, rangers and the growers themselves acknowledged that cocoa plantations are spreading illegally into protected areas of the reserve.

Farmers, some of which do not have access to fresh water in their homes, say they move there because their cocoa trees in other parts of the west African country are ageing and not producing as much.

The investigation comes as the global chocolate market is predicted to grow from a value of $48 billion (£38bn) in 2022 to nearly $68bn (£54bn) by 2029, according to analysts at Fortune Business Insights.