Scarlett Johansson has quit as an Oxfam ambassador after refusing to end her advertising relationship with Sodastream, amid a row over the Israeli company, which has a factory in a West Bank settlement.
"Scarlett Johansson has respectfully decided to end her ambassador role with Oxfam after eight years," her spokesman told AP.
"She and Oxfam have a fundamental difference of opinion in regards to the boycott, divestment and sanctions movement.
"She is very proud of her accomplishments and fundraising efforts during her tenure with Oxfam."
Johansson has worked with Oxfam since 2005, becoming an ambassador in 2007. Oxfam said that it "respects the independence" of celebrity ambassadors, but that Johansson's role with Soda Stream was "incompatible with her role".
In a statement, the charity said: "Oxfam believes that businesses, such as SodaStream, that operate in settlements further the ongoing poverty and denial of rights of the Palestinian communities that we work to support. Oxfam is opposed to all trade from Israeli settlements, which are illegal under international law."
Johansson will make her debut appearance in a SodaStream advert during the ad break in the Superbowl this weekend.
Before quitting as an ambassador, Johansson blogged about the issue for The Huffington Post, saying she was "a supporter of economic cooperation and social interaction between a democratic Israel and Palestine".
She said the company was committed to "building a bridge to peace between Israel and Palestine, supporting neighbours working alongside each other, receiving equal pay, equal benefits and equal rights. That is what is happening in their Ma'ale Adumim factory every working day."
She continued: "As part of my efforts as an Ambassador for Oxfam, I have witnessed first-hand that progress is made when communities join together and work alongside one another and feel proud of the outcome of that work in the quality of their product and work environment, in the pay they bring home to their families and in the benefits they equally receive."
SodaStream unveiled Scarlett Johansson as its first-ever Global Brand Ambassador
Johansson said she "trusts that the consumer will make their own educated choice" and that she was "happy that light is being shed on this issue in hopes that a greater number of voices will contribute to the conversation of a peaceful two state solution in the near future".
SodaStream's factory is on occupied territory, in the West Bank settlement of Ma'ale Adumim, employing around 500 Palestinians and 350 Israeli Jews.
Pro-Palestinian campaigners say that the presence of the factory normalises the occupation of the West Bank and promotes a boycott of Israeli companies that operate there.
"Settlements and occupation will never lead to peace," the head of the Palestinian Workers Union, Shaher Saad, told Reuters. "I support a boycott that will lead to these lands and means of economic growth returning to Palestinian ownership."
This article originally stated the SodaStream factory employed 900 Palestinians. The company has since stated the actual figure is 500.