Of all the people who have turned on Facebook CEO Mark Zuckerberg, this may be the biggest yet.

Brian Acton, co-founder of the internationally popular WhatsApp messaging service, sent out a tweet from his unverified Twitter account late Tuesday telling people "It is time. #deletefacebook." 

Earlier in the day, the #DeleteFacebook hashtag trended in the wake of accounts that Facebook user information landed in political advertisers' hands without the consent of users.

Acton's tweet is a notable move considering he sold WhatsApp to Facebook for $19 billion in 2014 and worked there until late last year. WhatsApp was founded in 2009.

Facebook has come under increasing fire for mishandling its user data. A series of reports in The New York Times, Observer and UK's Channel 4 said University of Cambridge lecturer Aleksandr Kogan and a political data analytics firm called Cambridge Analytica worked together to leak information on more than 50 million user profiles from Facebook. Facebook learned of the effort in 2015, but didn't discuss it publicly until last Friday.

Since then, the company has faced criticism on all fronts, particularly for Zuckerberg's noted silence, defensive tweets by executives and legal threats toward the Guardian.

Acton did not respond to a request for comment. Facebook declined to comment.

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