Ride service Lyft on Thursday asked a U.S. judge to prevent its biggest rival, Uber, from making further demands for confidential information, as part of a case about a data breach that affected as many as 50,000 Uber drivers.

In court documents filed in the litigation, Lyft called Uber's data request an attempt "to conduct its own witch-hunt" and "to dig into its competitor's internal, confidential and trade-secret information."

Lyft's motion marks the startup's public entry into a civil lawsuit over the May 2014 data breach, which Uber has tied to a Lyft employee.

Uber has subpoenaed a wide breadth of information from the Lyft employee, including communications with any Uber drivers and passengers, web browsing activity around the time of the hack, and documents related to "any scraped, crawled, spidered, copied, downloaded or otherwise accessed from Uber's computers, servers, or services."

The employee has not been named in court documents, but two sources told Reuters in October the Comcast IP address that had access to a security key used in the breach was assigned to Lyft's technology chief, Chris Lambert.

(Reporting by Heather Somerville and Dan Levine; Editing by Sandra Maler and Leslie Adler)