A number of supermarkets have removed some coconut water and oil from their shelves after it emerged the products were made with fruit picked by monkeys.
The monkeys are snatched from the wild and trained to pick up to 1,000 coconuts a day, People for the Ethical Treatment of Animals (Peta) said.
The animal rights group said pigtailed macaques in Thailand were treated like «coconut-picking machines».
In response Waitrose, Ocado, Co-op and Boots vowed to stop selling some goods.
Meanwhile, Morrisons said it had already removed products made with monkey-picked coconuts from its shelves.
In a statement, Waitrose said: «As part of our animal welfare policy, we have committed to never knowingly sell any products sourced from monkey labour.»
Co-op said: «As an ethical retailer, we do not permit the use of monkey labour to source ingredients for our products.»
In a tweet, the prime minister’s fiancée Carrie Symonds, a conservationist, welcomed the announcements from the supermarkets.
She called on all other supermarkets to boycott the products.
«I’m told Asda, Tesco & Sainsbury’s STILL (sic) sell such products,» she said.
Sainsbury’s said: «We are actively reviewing our ranges and investigating this complex issue with our suppliers.»
Asda and Tesco did not immediately respond to the BBC’s request for comment.
1,000 coconuts a day
Peta said it had found eight farms in Thailand where monkeys were forced to pick coconuts for export around the world.
Male monkeys are able to pick up to 1,000 coconuts a day, Peta says. It’s thought that a human can pick about 80.
It said it also discovered «monkey schools», where the animals were trained to pick fruit, as well as ride bikes or play basketball for the entertainment of tourists.
«The animals at these facilities – many of whom are illegally captured as babies – displayed stereotypic behaviour indicative of extreme stress,» Peta said.
«Monkeys were chained to old tyres or confined to cages that were barely large enough for them to turn around in.»
«One monkey in a cage on a lorry bed was seen frantically shaking the cage bars in a futile attempt to escape, and a screaming monkey on a rope desperately tried to run away from a handler.»
In one case, the organisation was told that monkeys would have their canine teeth pulled out if they tried to bite handlers.
«These curious, highly intelligent animals are denied psychological stimulation, companionship, freedom, and everything else that would make their lives worth living, all so that they can be used to gather coconuts,» said Peta director Elisa Allen.
«Peta is calling on decent people never to support the use of monkey labour by shunning coconut products from Thailand.»