Democratic Sen. Mark UdallMark Emery UdallTrump calls Kavanaugh accusations ‘totally political’ Record number of LGBT candidates running for governor Senate GOP rejects Trump’s call to go big on gun legislation MORE (Colo.) on Sunday expressed skepticism that the National Security Agency’s massive phone tracking program was really necessary to help the government thwart possible terrorist attacks. 

"My concern is that this is vast," Udall said of the phone data collection program in an interview on CNN's “State of the Union.” "It hasn't been proven that it works, uniquely. It hasn't been proven to have disrupted plots. Finally it's only another step to take that computer and involve human beings to take another look at it. 

Udall said it was unclear if other government efforts could have successfully prevented terrorism without resorting to such a breach of privacy.

"I think the data is unclear," Udall said. "It's unclear to me that we've developed any intelligence through the metadata program that's led to the disruption of plots that we couldn't have developed through other data in other intelligence."


Udall's comments come days after the disclosure of two surveillance programs, one which provided the government with phone numbers and metadata on calls and another program which obtained information on foreign Internet users.

Critics have questioned the privacy implications of the programs, painting them as an unnecessary overreach. but the administration has defended them as critical to national security.

President Obama defended the programs saying that the programs were not being abused and have been necessary in preventing terrorism plots.  

Administration officials say lawmakers were briefed and the leaders of the Intelligence panels have backed the programs. But many in Congress say they were not told about the full extent of the NSA’s surveillance.

"It's the scale of this that really concerns me and the fact that the American public doesn't know about it,” said Udall. 

In a separate interview on ABC's This Week Udall said he believed the administration had been forthcoming about the programs since their disclosure by the press

“This is the law, but the way the law is being interpreted has really concerned me,” said Udall. “The law has been interpreted in a secret way.  That’s what I’ve been calling for is let’s have full disclosure of how this law is being applied.  

“This isn’t a scandal, but this is deeply concerning to me and a lot of Americans, and frankly a lot of my colleagues in the Senate on both sides of the aisle," he added.

This story was updated at 10:01 a.m.