(Reuters) - A divided U.S. appeals court said Meta Platforms must face a class action by advertisers that accused the Facebook and Instagram owner of overcharging them by fraudulently inflating the number of people their ads might reach.

In a 2-1 decision, the 9th U.S. Circuit Court of Appeals in San Francisco said advertisers could sue for damages as a group over Meta's claims about the "potential reach" of their ads.

Advertisers said the metric measured the number social media accounts, not the lower number of actual people, and inflated the number of potential viewers by as much as 400%.

The San Francisco-based appeals court also decertified a separate class seeking injunctive relief, meaning the advertisers cannot sue as a group, because it wasn't clear that the main plaintiff had legal standing to sue.

A dissenting judge would have decertified both classes.

Meta and its lawyers did not immediately respond to requests for comment.

The Menlo Park, California-based company has said ads generate "substantially all" of its revenue, which totaled $134.9 billion in 2023. Net income was $39.1 billion.