WASHINGTON - Sen. Al Franken began a hearing on mobile privacy with Apple and Google by calling the companies "brilliant." At its conclusion, however, he sounded unconvinced the two tech giants are taking customer privacy seriously enough.

"People have a right to know who is getting their information and a right to decide how that information is shared and used," the Minnesota Democrat said as the session ended on Tuesday. "I still have serious doubts that those rights are being respected in law or in practice."

The hearing -- Franken's first as chairman of the new privacy, technology and law subcommittee -- was sparked in part by an outcry after a report last month that Apple was storing detailed location data on users' phones. Google's Android phones collect similar location data.

Apple and Google executives defended their privacy policies at Tuesday's hearing, saying that users opt-in to using location-based services and other data that are shared with third parties. "Apple is deeply committed to protecting the privacy of all of our customers," said Guy Tribble, Apple's vice president of software technology. "Apple does not track users' locations."

Much of the hearing focused on mobile applications, which use location data for things such as providing navigation or finding the closest store. Franken pressed the company witnesses about why they don't require third-party applications to have privacy policies that let users know who has access to personal data. He asked them to require apps have a "clear, understandable privacy policy."

Both Tribble and Google director of public policy Alan Davidson said they would make the suggestion to their top management.

Other senators moved beyond privacy to question Apple and Google about other issues. Sen. Richard Blumenthal, D-Conn., asked Google about the "WiSpy" incident, in which the company collected personal data through the Street View cars it uses for mapping. Sen. Charles Schumer, D-N.Y., bashed Apple and Google for not shutting down applications that tell users where drunken-driving checkpoints are located.

While Franken says he plans to introduce legislation to strengthen privacy laws, he emphasized on Tuesday that he doesn't want to prevent smartphones from offering location-based services. Calling them "incredible," he said no one is trying to stop Apple and Google from making their products.

"I love that I can use Google Maps, for free no less," Franken said, "and the same for the app on my iPad that tells me the weather."

The debate over mobile privacy is focused on location data because people carry phones with them nearly all the time. Apps such as Google Maps need access to detailed location information in order to function -- but that's also valuable data to advertisers.

The danger, Franken said, is that data can also be used for illicit purposes. He cited a Justice Department report that found more than 26,000 people are stalked through GPS annually. "When I sent a letter to Apple to ask the company about its logging of users' location," Franken said, "the first group to reach out to my office was the Minnesota Coalition for Battered Women."

Jeremy Herb • 202-408-2723 Twitter: @StribHerb