The National Security Agency’s massive collection of Americans’ phone records has “played little or no role” in the disruption of dozens of terrorist plots, contrary to Obama administration assertions, said two U.S. senators who have access to classified information.

In a statement Wednesday, Sens. Ron Wyden (D-Ore.) and Mark Udall (D-Colo.) disputed recent statements by senior administration officials that a top-secret NSA surveillance program to collect tens of millions of domestic calling records from U.S. phone companies has helped thwart more than 50 terrorist plots in the United States and abroad.

The phone-records program, authorized under Section 215 of the USA Patriot Act, was revealed this month after a leak to the Guardian newspaper. Details of a separate program to collect e-mails and other Internet content of foreign targets were also disclosed this month following leaks to the Guardian and The Washington Post.

Both programs, NSA Director Keith B. Alexander said this week, have provided the government with “critical leads” to foil plots, including one to bomb the New York Stock Exchange. He testified to Congress that the Internet program contributed to plot disruptions in “over 90 percent” of the cases.

Wyden and Udall, both members of the Senate Intelligence Committee, acknowledged that “multiple terrorist plots have been disrupted at least in part because of information” from the Internet surveillance program, which is known as PRISM and is authorized under the Foreign Intelligence Surveillance Act.

But, they said, “saying ‘these programs’ have disrupted ‘dozens of terrorist plots’ is misleading if the bulk phone-records collection is actually providing little or no unique value.”

They said it is unclear why federal agents do not simply obtain a court order for the phone records of individual terrorist suspects rather than creating a massive government database of records.

Government officials say that having a lawful database at their fingertips provides more agility than having to demand suspects’ records from companies through individual court orders. They say that they search the database only when they have “reasonable suspicion” that the target is linked to terrorism.

“It may be more convenient for the NSA to collect this data in bulk, rather than directing specific queries to the various phone companies,” said the senators, who have introduced a bill to limit the surveillance. “But in our judgment, convenience alone does not justify the collection of the personal information of huge numbers of ordinary Americans if the same or more information can be obtained using less obtrusive methods.”