WASHINGTON - The Government Accountability Office has recommended development of specific federal rules and deadlines for cellphone companies and mobile device manufacturers that would protect customers from having their locations shared with others without their knowledge.

Cellphone technology now includes global positioning systems and other applications that determine people's exact locations on an ongoing basis. How companies use that data without customers' knowledge has been a cause for concern among privacy advocates.

"The lack of clear disclosures to consumers about how their location data are used and shared means that consumers lack adequate information to provide informed consent about the use of these data," the GAO concluded in a new report requested by U.S. Sen. Al Franken.

The Minnesota Democrat chairs the Senate Judiciary Committee's Subcommittee on Privacy, Technology and the Law. He has held hearings and expressed concerns about people's private information being shared without their knowledge or consent.

The new report "very clearly makes the case for regulation," Franken said in an interview Wednesday. "It says when people get [cellphone applications], their location gets taken and shared with third parties and people don't know that."

While acknowledging that location data helps companies provide better services to consumers, the GAO expressed concern that the collection of location data risks the disclosure "to unknown third parties for unspecified uses, consumer tracking, identity theft, threats to personal safety and surveillance."

Franken said some applications are designed and marketed as "stalking apps" that have been used by abusive spouses or boyfriends to track the whereabouts of their abused partners.

Legislation that Franken introduced in the Senate would make stalking apps illegal and would "require companies to get your permission before they get your location information or share it with a third party." It is now pending before the judiciary committee.

What concerned GAO investigators most was the lack of mandatory standards for handling location data. The mobile industry has suggested ways of disclosing what personal customer information it collects and who it distributes that information to. But the watchdog agency concluded that the industry applies the voluntary standards inconsistently.

The GAO interviewed mobile phone companies, device manufacturers, application developers and federal agencies.

In the end, GAO decided cellphone owners are "unable to adequately judge whether the companies with which their data are shared are putting their privacy at risk."

The GAO recommended the Department of Commerce "develop specific goals, time frames, and performance measures" for the mobile information industry. It also called on the Federal Trade Commission to tell the industry what it thought were "appropriate actions by mobile companies with regard to protecting mobile location data privacy."

Jim Spencer • 202-383-6123