The Obama administration has defended its gathering of phone records of millions of Verizon customers—right down to local call data—after the Guardian newspaper reported late Wednesday night that the National Security Agency has been collecting them under a top-secret court order issued in April. The administration called it a "critical tool" against terrorism and underlined that the government is not listening in on anyone's calls.

Under the Foreign Intelligence Surveillance Court order, the Guardian reported, Verizon Business Services must provide the NSA “on an ongoing daily basis” with information from calls between the U.S. and overseas—as well as from calls made entirely inside the U.S. Calls made entirely overseas were not affected. It was unclear whether phones in other Verizon divisions—its regular cellphone operations, for instance—were similarly targeted.

Guardian writer Glenn Greenwald, a frequent and fierce critic of the national security state’s expansion since 9/11, writes in his bombshell report that:

The document shows for the first time that under the Obama administration the communication records of millions of US citizens are being collected indiscriminately and in bulk—regardless of whether they are suspected of any wrongdoing.

The order, issued April 25 and valid through July 19, requires Verizon to turn over the numbers of both parties, location data, call duration and other information—though not the contents of the calls.

The White House initially declined to comment, but a senior administration official has now defended the activities described in the Guardian piece without confirming the specific report.

"On its face, the order reprinted in the article does not allow the government to listen in on anyone's telephone calls," the official, who requested anonymity, wrote in an email. "The information acquired does not include the content of any communications or the name of any subscriber."

And "information of the sort described in the Guardian article has been a critical tool in protecting the nation from terrorist threats to the United States, as it allows counterterrorism personnel to discover whether known or suspected terrorists have been in contact with other persons who may be engaged in terrorist activities, particularly people located inside the United States," the official said.

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Congress has been "regularly and fully briefed" on such practices, which occur under a "robust legal regime" and "strict controls and procedures ... to ensure that they comply with the Constitution and laws of the United States and appropriately protect privacy and civil liberties," the official added.

Judge Roger Vinson’s order relies on Section 215 of the Patriot Act. That part of the law, also known as the “business records provision,” permits FBI agents to seek a court order for “any tangible things (including books, records, papers, documents, and other items)” it deems relevant to an investigation.

Democratic Sen. Ron Wyden of Oregon, who sits on the Senate Intelligence Committee, has repeatedly sounded the alarm about the way the government interprets that provision—though he's sharply limited in what he can say about classified information. Wyden and Democratic Sen. Mark Udall of Colorado, another committee member, wrote a scathing letter to Attorney General Eric Holder in September 2011 warning that Americans would be "stunned" if they learned what the government was doing.

The American Civil Liberties Union denounced the scope of the surveillance. "It’s analogous to the FBI stationing an agent outside every home in the country to track who goes in and who comes out," said Jameel Jaffer, ACLU deputy legal director. The organization's legislative counsel, Michelle Richardson, bluntly branded the surveillance "unconstitutional" and insisted "the government should end it and disclose its full scope, and Congress should initiate a full investigation."

And former Vice President Al Gore sharply condemned the government's actions on Twitter: