The company's executives continued the campaign with another video meeting with advertisers late on Tuesday, AEST, followed by separate sessions with ad holding companies. At the meeting Facebook's marketing chief Carolyn Everson, public policy director Neil Potts, and vice president for integrity Guy Rosen, took a more conciliatory tone, acknowledging clients' concerns about ads appearing next to hate speech and misinformation, said four people with knowledge of the event.

Yet even as Facebook has laboured to stanch the ad exodus, it is having little effect. Executives at ad agencies said that more of their clients were weighing whether to join the boycott, which now numbers more than 300 advertisers and is expected to grow.

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The push from advertisers has led Facebook's business to a precarious point. The Silicon Valley company has never faced a public backlash of this magnitude from its advertisers, whose spending accounts for more than 98 per cent of its annual $US70.7 billion ($101.3 billion) in revenue.

"Their intentions are good, but their judgment is poor," David Jones, a top advertising executive, said of Facebook. Jones, who was a founding member of Facebook's client council — a group of ad executives who advise the company — said if the social network did not make further progress on hate speech, then "they're starting down a long slippery slope to being irrelevant."