June 6, 2013 -- The Obama administration has been quietly collecting millions of telephone records from U.S. Verizon customers under a top-secret court order first obtained in late April, according to British newspaper The Guardian.

A copy of the classified order, posted Wednesday on the newspaper's website, reveals that Verizon has been required to provide to the National Security Agency on an "ongoing, daily basis" information on all phone calls made through its systems.

Under the order, the government has obtained phone numbers of both parties on every Verizon call, the call's duration, location data and the time of day the calls were made. The order does not allow the government to listen in on the calls or obtain details of their contents.

The order was granted April 25 by the Foreign Intelligence Surveillance Court (FISA), which oversees secret government requests for private information that might help identify suspected terrorists or foreign nationals in the U.S. The order, which did not identify intended targets or the rational for casting such a wide net, expires July 19.

READ: Senators Dismiss Verizon Phone Record Dragnet

A former top U.S. intelligence official with decades of direct experience handling FISA surveillance matters told ABC News that the scope of the Verizon order posted online by the Guardian is breathtaking.

"This suggests NSA is collecting broadly," the former intelligence official told ABC News. "Collection does not necessarily mean review, but it still would be a large change even from post-9/11 activity."

Another official, Mark Rossini, a former senior FBI official detailed to CIA, said a program such as this would collect numbers in a massive database that is merged with all the telephone data the NSA vacuums up from around the globe. The NSA then correlates the information to see "any links or patterns of activity" related to subjects of U.S. investigation.

"This pertains to terrorism, spying, industrial espionage, cyber, etc.," said Rossini, who was once a top briefer to former CIA Director George Tenet. "This is all done to keep America safe and economically secure and ahead."

The veracity of the Guardian's document could not be independently confirmed by ABC News. Neither the NSA nor Verizon responded to requests for comment, though neither immediately denied the report.

Randy Milch, Verizon Executive Vice President and General Counsel, addressed The Guardian report in an email to employees, obtained by ABC News.

"We have no comment on the accuracy of The Guardian newspaper story or the documents referenced," he said. "Verizon continually takes steps to safeguard its customers' privacy. Nevertheless, the law authorizes the federal courts to order a company to provide information in certain circumstances, and if Verizon were to receive such an order, we would be required to comply."

A senior Obama administration official also declined to verify the authenticity of the order posted by the Guardian, but defended such data collection as a "critical tool" to protect the country.

"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," the administration official said. "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."

Rep. Mike Rogers (R-Mich.), Chairman of the House Intelligence Committee, told reporters the NSA program helped thwart a "significant domestic terrorist attack... within the last few years."

But the revelation also appears to call into question testimony from Director of National Intelligence Gen. James Clapper just three months ago, one month before the order was granted. Then, Sen. Ron Wyden (D-Ore.) asked Clapper if the NSA collected "any type of data at all on millions or hundreds of millions of Americans."

"No sir... Not wittingly," Clapper said. "There are cases where they could inadvertantly, perhaps, collect, but not wittingly."

Liberal activists responded strongly to the Guardian report. Former Vice President Al Gore called "blanket surveillance obscenely outrageous" and the American Civil Liberties Union called the practice "alarming."

"It is beyond Orwellian, and it provides further evidence of the extent to which basic democratic rights are being surrendered in secret to the demands of unaccountable intelligence agencies," ACLU deputy legal director Jameel Jaffer said.

A large grassroots group -- the Progressive Change Campaign Committee -- also launched an "emergency petition" demanding an immediate congressional investigation of the Obama administration.

Attorney General Eric Holder, who was already scheduled to appear before a Congressional committee today, declined to go "into anything specific" with the lawmakers, but told them members of Congress have been "fully briefed" on the issue. Holder agreed to testify before another committee in a classified setting about the program.

White House spokesperson Josh Earnest told reporters travelling on Air Force One that the president welcomes the debate over the NSA program.

"The president welcomes the discussion of the trade-off," Earnest said, referring to the tension between national security and personal liberty.

READ MORE: The Politics of the Verizon/NSA Controversy

ABC News' Lee Ferran, Sunlen Miller, Abby Phillips and Z. Byron Wolf contributed to this report.