(c) 2013, Bloomberg News.

(c) 2013, Bloomberg News.

WASHINGTON Senate Intelligence Committee Chairman Dianne Feinstein opposes requiring phone companies to retain surveillance records now given to the National Security Agency.

The California Democrat decided it would be too costly and complex for companies to maintain the data after reviewing an NSA analysis of how it would work, according to a committee aide who wasn't authorized to speak on the record.

"Senator Feinstein opposes storing the metadata with the telecommunication companies themselves," her spokesman, Brian Weiss, said in a statement.

Feinstein's opposition is a major obstacle for lawmakers who see the proposal as a way to quell the public furor over U.S. spying, since her panel oversees the NSA. While no legislation has been introduced, the telecommunications industry has been lobbying Congress and President Barack Obama's administration to defeat the idea before an expected debate next month on curbing the NSA's powers.

"If the government needs it, then the government should figure out how to safeguard it," said Jot Carpenter, vice president of government affairs for CTIA-The Wireless Association, a Washington-based trade group that represents the wireless industry. Companies don't want "to be the custodian of that information for any longer than we need it."

Some lawmakers and privacy advocates suggested companies retain the bulk phone records after the NSA program was exposed by former contractor Edward Snowden. Under the program, phone numbers and call durations on millions of Americans are kept for five years under a secret court order.

Proposals already introduced in the House and Senate would require the NSA to get a warrant to search or obtain phone metadata. The alternative approach would allow the NSA to query databases kept by the carriers.

The NSA now retains the records in a central database. It can query them only when analysts have reasonable suspicion to believe a phone number is linked to a terrorist plot, according to an Aug. 9 description published by the Obama administration.

Officials for New York-based Verizon have expressed their concerns to the administration and lawmakers about being required to keep the metadata, spokesman Ed McFadden said in a phone interview. He declined to elaborate.

Spokesmen Michael Balmoris of AT&T and Anne Marshall of T- Mobile US Inc. declined to comment.

The NSA analysis presented to Feinstein found that compelling the phone companies to retain the data would come at a significant cost, the aide said in a phone interview.

It said the administration probably couldn't compel the companies to keep the data without legislation from Congress, the aide said.

The analysis didn't draw a conclusion, as that's a matter for policy makers to decide, the aide said. The aide declined to reveal the cost estimate or other details of the analysis.

Companies would expect Congress to give them immunity from privacy lawsuits over data breaches, Carpenter said. Costs include setting up server farms to store the data and buying software to protect the data and make it searchable, he said.

"You're talking about a very significant volume of data" and the carriers don't "want to be in a situation where they have to retain data any longer than necessary for their own business purposes," Carpenter said.

Some lawmakers still favor requiring phone companies, rather than the NSA, to retain the data and that may not change with Feinstein's opposition. Private storage would be less invasive of Americans' privacy rights because their recordkeeping practices are known to customers, said Rep. Adam Schiff, D-Calif. and member of the House intelligence committee.

"There's no reason the government needs to acquire all the data if it can get what it needs by querying the telecommunications providers," Schiff said, who has led calls in Congress to compel the companies to retain the data.

The proposal also has been raised by the Privacy and Civil Liberties Oversight Board, a panel of citizens established to ensure U.S. spy programs have appropriate privacy safeguards.

The Obama administration hasn't yet weighed in on the proposal. Obama remains open to changes in the phone metadata collection program, which is carried out under Section 215 of the USA Patriot Act, Caitlin Hayden, a White House spokeswoman, said in a statement.

"He believes that we can take steps to put in place greater oversight, greater transparency, and constraints on the use of this authority and looks forward to working with the Congress," she said.

Snowden, the former NSA contractor now in Russia under temporary asylum, exposed a classified legal order compelling Verizon to turn over the phone records of millions of customers to the NSA for use in counterterrorism operations. The records played a role in preventing 12 terrorist attacks inside the U.S., General Keith Alexander, the NSA Director has said.

A May 2012 internal audit leaked by Snowden found 2,776 cases of violations in the preceding year in collecting voice and data communications of both Americans and foreigners. Legal opinions declassified Aug. 22 show the NSA improperly intercepted as many as 56,000 Internet communications by Americans a year between 2008 and 2011 until the Foreign Intelligence Surveillance Court ordered the practice stopped.