“Press reports that the National Security Agency broke privacy rules thousands of times per year and reportedly sought to shield required disclosure of privacy violations are extremely disturbing,” House Minority Leader Nancy Pelosi (D-Calif.) said. She said Congress should take steps to ensure that such incidents are not repeated.

Two leading critics of the surveillance programs said Friday that the administration has long underplayed the programs’ impact on privacy. “We believe Americans should know” that the report of violations “is just the tip of a larger iceberg,” Sens. Ron Wyden (D-Ore.) and Mark Udall (D-Colo.) said in a statement.

They also said they “appreciate the candor” of the Foreign Intelligence Surveillance Court chief judge “regarding the court’s inability” to independently verify statements made by the executive branch. The senators are among a number of lawmakers who have sponsored legislation that would limit the scope of the NSA’s surveillance and require stronger oversight.