SAN FRANCISCO - Brian Acton, a co-founder of WhatsApp, which Facebook bought in 2014, on Tuesday (March 20) urged people to delete their accounts on the giant social network, USA Today reported.

"It's time," tweeted Acton, who quit Facebook earlier this year to start a foundation. He added the hashtag #DeleteFacebook.

WhatsApp declined to comment.

According to The Verge, it was unclear whether Acton's feelings about Facebook extend to his own app. But last month, Acton invested US$50 million (S$66 million) into Signal, an independent alternative to WhatsApp.

His latest comment comes amid growing public outrage over the misuse of the private information of tens of millions Facebook users by Cambridge Analytica, the firm that claimed it helped US President Donald Trump in the 2016 presidential election.

Shares of Facebook, Twitter and Snapchat owner Snap fell further on Tuesday as Wall Street fretted over potential regulatory scrutiny that could hobble the business of the social networks.

Facebook lost 2.6 per cent after it said it faced questions from the US Federal Trade Commission about how its users' personal data was mined by a political consultancy hired by Trump's campaign. Facebook shares had already tumbled 6.8 per cent on Monday.

Since revelations on Saturday that a political consulting firm had improperly obtained personal data on 50 million Facebook users, the world's largest social media company has lost US$60 billion of its stock market value.

In 2014, Facebook bought WhatsApp for US$16 billion from its co-founders Jan Koum and Acton. Koum continues to lead the company,

Acton is not the first former Facebook executive to express unease about the company after leaving it. Last year, former head of growth Chamath Palihapitiya caused a firestorm after saying "we have created tools that are ripping apart the social fabric of how society works", The Verge reported.

Other former executives to express regrets include Sean Parker, Justin Rosenstein, and investor Roger McNamee.