Protesters dressed as orangutans have demonstrated against Nestle's use of palm oil in their products outside the company's factory in York.
They say Indonesian farmers cut down the orangutans' rainforest habitat to make way for the palm plants.
Greenpeace campaigners also scaled the company's headquarters in Croydon, south London.
Nestle said it has sought assurances from its suppliers about the supply chain of the palm oil it used.
The protest follows a Greenpeace report detailing Nestle's use of palm oil.
The report claims palm oil used in Nestle products has come from a palm oil producer which is destroying the Indonesian rainforest.
Rich Claxton, of Greenpeace, said: "Nestle products like KitKats contain palm oil from suppliers who are trashing rainforests and driving orangutans to extinction.
"Other big companies are acting to stop this, but Nestle is turning a blind eye to it and continuing to trade with a company that has done more than any other to wipe out the rainforests of Indonesia.
"Nestle must stop destroying rainforests for palm oil."
Greenpeace also released a video showing an office worker trying to eat a KitKat but instead biting into an orangutan's finger.
In a statement, Nestle said it was committed to using only "certified sustainable palm oil" by 2015.
"As an important step on that journey, a number of Nestle markets, including Nestle UK, have already purchased Green Palm certificates, the certificate trading programme designed to help suppliers tackle the environmental and social problems created by the production of palm oil."