This is pretty damn incredible:

The chairwoman of the Senate intelligence committee on Tuesday accused the Central Intelligence Agency of improperly removing documents from computers that committee staff members had been using to complete a report on the agency’s detention program, saying the move was part of an effort to intimidate the committee.

Senator Dianne Feinstein, Democrat of California and the chairwoman of the committee, suggested on the Senate floor that the agency had violated federal law and said the C.I.A. had undermined Congress’s constitutional right to oversee the actions of the executive branch.

“I am not taking it lightly,” she said.

John O. Brennan, the C.I.A. director, denied Ms. Feinstein’s assertions on Tuesday. “Nothing could be further from the truth,” Mr. Brennan said in response to questions from NBC’s Andrea Mitchell in an appearance at the Council on Foreign Relations in Washington. “We wouldn’t do that. I mean that’s just beyond the scope of reason in terms of what we would do.”

More, from the Washington Post:

Meanwhile, a letter that Brennan distributed to the CIA workforce on Tuesday raised questions about Feinstein’s claims and her awareness of how and when the committee obtained the so-called Panetta review files.

The letter, which Brennan sent to Feinstein on Jan. 27 and which was attached to a message he sent the workforce, recounts a meeting they had weeks earlier to discuss the matter. During that meeting, Feinstein said she didn’t know that the committee already had copies of the Panetta review. Brennan pushed her to explain why the panel had recently requested the files when they were already in its possession.

“You informed me that you were not aware that the committee staff already had access to the materials you had requested,” Brennan wrote, according to a copy obtained by The Washington Post. Brennan urged Feinstein to work with the agency to determine how the committee had obtained the documents, a request she ultimately rejected, officials said.

The CIA began to suspect that the panel had obtained those files this year after lawmakers referred to the supposed “internal review” publicly. U.S. officials said CIA security personnel then checked the logs of the computer system it had set up for the committee, and found that the files had been moved to a part of the network that was off-limits to the CIA.

“They did something to get those documents,” said a U.S. official briefed on the matter. A security “firewall was breached. They figured out a workaround to get it.” The official declined to elaborate.

OK, but the allegation here, one leveled by the most senior US Senator on intelligence matters, one who has been very quick to defend aggressive intelligence gathering, is that the US spy agency spied on the US Congress.