Nestle has been accused of failing to carry out basic checks at its cocoa farms in Ivory Coast, where child labour and abuse are widespread.
The company says tackling the problem is now a high priority.
The Fair Labor Association said on Friday it had found multiple serious violations of Nestle's supplier code, often because there are no local laws to provide fair and safe working conditions.
The Washington organisation said health and safety problems were rampant. It said many people were injured by machetes used to cut cocoa and that children and adults were subject to abusive working practices.
Nestle buys around 10% of the cocoa crop of 1.3 million tonnes there.