SAN FRANCISCO — After facing allegations from Uber that it nurtured online advertising fraud to extract millions of dollars, the global advertising firm Fetch Media Ltd. has fired back with a new lawsuit that accuses Uber of forum-shopping and evading its bills.

Uber Technologies Inc. sued Fetch in September for $50 million claiming it was charged for mobile ads by Fetch that never generated returns. The lawsuit landed in front of U.S. District Judge Yvonne Gonzalez Rogers of the Northern District of California.

In a complaint filed Tuesday, Fetch's attorneys at Quinn Emanuel Urquhart & Sullivan said that now Uber is attempting to drop that suit after drawing Rogers, and instead seeking to litigate its claims in a separate ongoing proceeding in California state court.

“Fetch does not believe that Uber can so easily escape federal court scrutiny of its theories,” the complaint said. The suit seeks declaratory judgment that Fetch did not breach its advertising services agreement with Uber, and that it is owed some $19 million in unpaid invoices.

Underlying the spat are accusations by Uber that the advertising suppliers Fetch contracted with to display mobile ads promoting Uber used technological tricks to artificially inflate the number of people who clicked the ads and downloaded Uber's ride-hailing app.

While Uber accuses Fetch of hiding that fraud, Fetch said it discussed the problem of ad fraud with Uber at length and that Uber declined to use tools that could effectively monitor for it. Then, Fetch alleges, personnel changes at Uber in January 2017 led to finger-pointing when Uber began using analytics to track ad behavior.

The advertising company also argues it had no responsibility “to police and prevent ad fraud” by third-party suppliers. “Uber seeks to blame Fetch for the risks it took on, and for responsibilities Fetch never had, advancing an incorrect interpretation of Fetch's responsibilities under the [services agreement],” the complaint added.

Uber's lead counsel in the case, Reed Smith partner John Bovich, did not immediately respond to requests for comment on Wednesday. Uber also did not immediately respond to email inquiries about the new lawsuit.

Uber filed its motion to voluntarily dismiss its case in federal court against Fetch on Dec. 22. Fetch is seeking to relate its new case against Uber to that original suit—which would put the litigation back in Rogers' courtroom. Rogers granted Uber's motion to dismiss its case without prejudice on Wednesday afternoon.

The ongoing state court case is currently pending in San Francisco Superior Court and originated when a company called Phunware Inc., represented by Wilson Sonsini Goodrich & Rosati, sued Uber for over $3 million in allegedly unpaid bills. Phunware was one of the suppliers hired by Fetch to conduct Uber's advertising campaign, according to its complaint.

In responding to that suit, Uber filed a cross-complaint against Phunware and named Fetch as a defendant as well. Fetch and Phunware are seeking to stay the state court case, pending the adjudication of the dispute in federal court. Their motion to stay is currently pending in front of San Francisco Superior Court Judge Harold Kahn.