The secret surveillance programs revealed last year by Edward Snowden brought a firestorm of domestic and international scorn to the American spy agencies, namely the NSA, because of their sweeping and seemingly indiscriminate collection of data many assumed was private.

Officials found themselves scrambling to decide which side of the fence to sit on. Jump too fast to rein in intelligence gathering, and one risks being seen as weak on terrorism or simply reactionary, but to defend them too strongly would invite public ire on a vastly unpopular program.

One of these defenders was Sen. Dianne Feinstein, D-Calif., the chairwoman of the Senate Intelligence Committee. When asked in 2013 about NSA phone-log monitoring that had just been revealed to the public, she responded, “I know that people are trying to get to us. This is the reason why the FBI now has 10,000 people doing intelligence on counterterrorism. It’s called protecting America.”

Feinstein’s previous comments on surveillance made her disclosure Tuesday all the more surprising. In a public address, she accused the CIA of breaking into computers used by the intelligence committee in its investigation into the agency’s controversial detention and interrogation program.

Feinstein contended that the CIA monitored the committee’s work, removed documents from the committee’s computers, and attempted to obstruct the investigation in what she called a “defining moment” for the oversight of the intelligence community, and a possible violation of federal law and the Constitution.

If Feinstein’s allegations are true, they would reveal a chilling reversal of the balance of power in government: elected representatives tasked with overseeing the spy agencies are being strong-armed out of their own investigation.

The potential motive is obvious: the Senate probe could reveal details of detention programs, created after 9/11, that some say use torture as an interrogation method. By suppressing this information, the CIA would ensure the programs remain secret.

CIA Director John Brennan said, “Nothing could be further from the truth” about Feinstein’s allegations. Brennan purportedly told Feinstein that agency personnel searched the computers because they believed the intelligence committee could have accessed materials the members were not authorized to see. Feinstein contends these materials were included in the collection provided to the committee.

Brennan’s denial echoes that of NSA Director Gen. Keith Alexander, who last year admitted to misleading the public on the number of terror attacks thwarted by mass surveillance programs. Alexander also mischaracterized the nature of the programs. When asked by Sen. Ron Wyden, D-Ore., on whether the NSA collects “any type of data at all on millions of Americans,” Alexander responded, “No, sir.”

In an interview with CNN, Wyden said he sees a pattern: “The fundamental question here is whether the Congress of the United States is going to be able to do effective oversight over the intelligence apparatus. And again and again … the intelligence leadership has, in effect, thwarted the ability of Congress to get the information it needs to do that oversight.”

The inner workings of spy agencies are necessarily opaque, and any oversight into their operations does need to balance the competing demands of accountability and secrecy. But if the CIA has been interfering in an official investigation to protect its own interests, it would be another disturbing example of a three-letter agency misleading or lying to the American public, of a surveillance state whose reach includes even those watching the watchers.