Twitter was sued by a shareholder over claims it misled investors on key growth metrics, including user count and user engagement, almost two years after touting plans to top 500m users.

The suit, filed on Friday in federal court in San Francisco in the US, comes as Twitter struggles to keep its audience from defecting to platforms such as Snapchat and Instagram.

Snapchat, the ninth-most-popular app in the US, surpassed 50m monthly mobile app users in April, besting Twitter for the first time, Bloomberg Intelligence analysts Jitendra Waral and Sean Handrahan said in an 18 August report, citing ComScore.

Shareholder Doris Shenwick claims Twitter executives misled investors on its growth prospects in November 2014, promising an increase in monthly active users to 550m in the “intermediate” term and more than a billion in the “longer term”.

The company failed to deliver on either estimate and concealed that it had no basis for those projections, the complaint said. As of 30 June, the company had 313m monthly active users, according to its website.

The lawsuit seeks class-action, or group, status to represent all shareholders who bought stock between 6 February 2015 and 28 July 2015. Twitter officials didn’t immediately respond to an e-mail seeking comment on the filing.

After several quarters of stagnant user growth and slowing sales, the San Francisco-based company is banking on re-engaging its users by letting them watch live video alongside tweets.

In one such move on 17 September, Twitter unveiled the first of 10 live streams in its much-hyped deal with the National Football League. CNBC reported that the first broadcast reached 2,1m viewers. — (c) 2016 Bloomberg LP