Snap, the owner of Snapchat, has been accused of inflating the number of users it has ahead of a possible initial public offering for $25 billion by a former employer.
Anthony Pompliano has alleged that he was "unlawfully" dismissed after just three weeks in September 2015 because he did not cooperate with the company on the scheme.
The lawsuit filed with Los Angeles County Superior Court said: "Snapchat has been falsely representing and continues to falsely represent to a wide range of entities and leaders in the social media industry that it terminated Mr Pompliano’s employment after a mere three weeks after he was hired because he was not adequately performing in his position at Snapchat.
"Such representations were false and malicious and made with the express of covering up Snapchat’s false representations to investors and the public."
Pompliano joined Snap in 2015 as a growth lead. He was previously a product manager at Facebook, responsible for growth and engagement.
A spokeswoman for Snap said in a statement that the claims were "totally made up by a disgruntled former employee."