Sen. Mark Udall (D-Colo.), who has emerged in recent days as one of the chief critics of the Obama administration’s surveillance programs, said Sunday that there’ s no proof that the National Security Agency's collection of Americans’ phone records has helped thwart any terror plots.

Udall, a member of the Senate Intelligence Committee, conceded that a separate program that monitors the Internet activity of foreigners -- code-named PRISM -- has paid dividends. But he said the collection of phone record metadata has not demonstrated that it’s effective.

“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 obtain through other programs,” Udall said on CNN’s “State of the Union.”

Udall said the Obama Administration should have been more transparent about its surveillance programs and that he doesn’t believe it’s protecting people's privacy.

“Maybe Americans think this is okay, but I think the line has been drawn too far towards we’re going to invade your privacy rather then we’re going to respect your privacy,” he said. “I expect the government to protect my privacy, and it feels like that isn’t what’s been happening.”