By Jeremy Pelofsky

WASHINGTON (Reuters) - The Congress should pass a law to give investigators freer access to cell phone records, an Obama administration official said on Thursday in remarks that raised concern among advocates of civil liberties and privacy.

The Supreme Court this year ruled a warrant was needed to put a GPS tracking device on a suspect's vehicle, prompting questions about other instances where probable-cause warrants were needed to obtain information in the rapidly changing world of mobile devices.

Federal courts around the country are split on whether to require warrants, said Jason Weinstein, a deputy assistant attorney general in the Justice Department's criminal division.

While prosecutors have been told to get warrants to put a tracking device on a vehicle, they should not be needed to obtain data from cell phone towers about the movements of a suspect, Weinstein said.

"There really is no fairness and no justice when the law applies differently to different people depending on which courthouse you're sitting in," he said at the "State of the Mobile Net" conference sponsored by the Congressional Internet Caucus Advisory Committee.

"For that reason alone, we think Congress should clarify the legal standard," he said, adding that being required to get a warrant at what he described as early stages of investigations would "cripple" prosecutors and law enforcement.

One civil liberties advocate sought to challenge that assertion, saying that the Obama administration made the same argument during the Supreme Court GPS case and it was soundly rejected.

"Not one justice accepted the Department of Justice's argument in that case. It got zero votes," Greg Nojeim, senior counsel at the Center for Democracy and Technology, said during the conference. "We're all here, the criminals are not taking over the country."

While some proposals have been made in Congress to address concerns and confusion about when a warrant is needed as new technologies emerge, the chances of legislation passing are considered slim because it is an election year and little legislation is expected to pass.

(Reporting by Jeremy Pelofsky; Editing by Howard Goller and Cynthia Osterman)