The company behind brands such as Ben and Jerry's, Dove and Marmite said it would halt US advertising on the social media platforms. Ad boycotts have led Facebook to institute a ban on hateful conduct and false claims.
Shares of Facebook and Twitter plummeted 7% on Friday following a decision from European consumer giant Unilever to pull US advertisements until the end of the year.
The Anglo-Dutch company, which is behind brands such as Ben and Jerry's ice cream, Dove soap, Lipton tea and Marmite spread, said Friday it was halting ads on Facebook, Twitter and Instagram in the United States due to the country's "polarized election period."
Twitter's vice president of global client solutions, Sarah Personette, said the company is "respectful of our partners' decisions and will continue to work and communicate closely with them during this time."
Unilever has joined a growing number of advertisers that have pulled back from online platforms after the Anti-Defamation League (ADL) called for the boycott as part of the "Stop the Hate for Profit" campaign.
On Thursday, American telecoms company Verizon joined a boycott on Facebook advertising. Last week, North Face, an outdoor clothing brand, became the first major marketer to participate in the boycott.
According to Axios, Unilever spent $2 million (€1.8 million) on Facebook advertising in June. The American news website said Proctor and Gamble, Unilever's main competitor, spent 10 times that amount this month and has yet to announce a similar boycott.
Facebook bans 'hateful conduct' in ads
Later Friday, Facebook founder and CEO Mark Zuckerberg announced his platform will flag all "newsworthy" posts from politicians that break its rules, including those from US President Donald Trump.
The new policy on hateful content will "prohibit claims that people from a specific race, ethnicity, national origin, religious affiliation, caste, sexual orientation, gender identity or immigration status are a threat to the physical safety, health or survival of others," Zuckerberg wrote on his Facebook page.
"We're also expanding our policies to better protect immigrants, migrants, refugees and asylum seekers from ads suggesting these groups are inferior or expressing contempt, dismissal or disgust directed at them."
Facebook is also banning false claims intended to discourage voting in the 2020 US elections. Zuckerberg had previously refused to take action against Trump posts suggesting that mail-in ballots will lead to voter fraud.
Social media companies have come under increasing pressure to monitor inflamatory posts and misinformation. Last month, Twitter put labels on Trump tweets for the first time, which drew ire from the US president.