Ben & Jerry’s has long been known for taking a public stance on social issues since it was founded in 1978, often backing campaigns on issues like LGBTQ+ rights and climate change.
In his letter Mr Greenfield said leaving the firm was “one of the hardest and most painful decisions” he had ever made but he could no longer “in good conscience” work for a business that had been “silenced” by Unilever.
This was despite an agreement that protected the brand’s social mission when it merged with the consumer goods giant 25 years ago, he said.
A spokesperson for The Magnum Ice Cream Company said the firm had been in dialogue with the two founders before Mr Greenfield’s decision to leave.
“We disagree with his perspective and have sought to engage both co-founders in a constructive conversation on how to strengthen Ben & Jerry’s powerful values-based position in the world,” they said.
