A key Senate Democrat believes that officials within the CIA disagreed with Director John Brennan’s approach during a heated battle between the spy agency and the Senate Intelligence Committee.

{mosads}Sen. Ron Wyden (D-Ore.) said in an interview for a new episode of HBO’s “Vice” that he believed lower-level staffers within the CIA disagreed with Brennan’s decision to search the Senate’s side of a walled-off computer network for classified documents.

“This will be the first time I’ve ever said this publicly: My sense is there were clearly people at the CIA who understood that what Mr. Brennan had done was flat out wrong,” said Wyden, a member of the Intelligence Committee and consistent critic of government spying efforts. “And they drafted an apology letter.

“And yet Mr. Brennan was just unwilling to publicly acknowledge wrongdoing.”

“We are the agency that is required by law to conduct vigorous oversight over the CIA,” Wyden claimed. “We can’t do vigorous oversight over the agency if the agency we’re supposed to be overseeing is in fact secretly searching our files.”

The battle between the CIA and the Senate Intelligence Committee came as part of a long-running investigation into the spy agency’s history of brutal interrogation techniques during the George W. Bush administration.

At some point while assembling that report, Senate staffers discovered secret CIA files dubbed the “Panetta review,” which the agency did not intend to hand over. When the CIA discovered what the Senate aides had in their possession, Brennan ordered officials to cross into the Senate side of a shared computer network to investigate.

The fight erupted into Congress when Sen. Dianne Feinstein (D-Calif.), then the Intelligence Committee chairwoman, accused the CIA of spying on its congressional overseers, a potentially unconstitutional act. Multiple lawmakers demanded Brennan resign, but two years later he has emerged relatively unscathed.

Wyden’s interview is set to air as part of a new Vice episode, “State of Surveillance,” on HBO on Friday evening.

For the episode, Vice co-founder Shane Smith traveled to Moscow to interview former National Security Agency contractor Edward Snowden, who is wanted on federal espionage charges in the U.S. after leaking documents in 2013 extensively detailing the NSA’s intelligence operation.