WASHINGTON — CIA Director John Brennan Tuesday denied allegations that his agency tampered with the network of senators investigating the CIA’s controversial detention and interrogation  program even as Sen. Dianne Feinstein sharpened her accusations, accusing the CIA of violating federal law and undermining Congress’ constitutional duty of oversight.

“Nothing could be further from the truth,” Brennan said in a rare public appearance Tuesday at the Council on Foreign Relations.

Feinstein, head of the Senate Intelligence Committee, accused the CIA of removing about 870 CIA documents from a computer network set up for senators as part of their investigation of the interrogation program from the Bush administration. Intelligence Committee staff also found a document written by the CIA that analyzed the committee’s review materials, which Feinstein argued is evidence of  CIA wrongdoing.

“I have grave concerns that the CIA’s search may well have violated the separation of powers principle embodied in the United States Constitution,” Feinstein said.

Started by the Bush administration in 2002, the CIA program, involving interrogations of suspected senior al-Qaida members that included techniques such as waterboarding and sleep deprivation,  has a history of secrecy.  Aside from the chairman and the vice chairman, members of the intelligence committee were not briefed about the program until September 2006, hours before President George W Bush revealed the program to the public.

The CIA inspector general and the Department of Justice are investigating this dispute.

“I defer to them to determine whether there was any violation of law or principle,” Brennan said.

When asked if he would resign if the CIA’s actions were found to be in the wrong, Brennan said he’d leave that decision up to the president. He maintained, however, that the CIA had done nothing wrong.

“When the facts come out on this I think a lot of people who are claiming there has been this tremendous spying and monitoring and hacking will be proved wrong,” Brennan said.

Feinstein also accused the CIA general counsel of filing a crimes complaint with the Justice Department against the Intelligence Committee staffers who found the CIA’s review document within the network established for the investigation. She also requested declassification of the Intelligence Committee’s oversight report.

“How Congress and how this will be resolved will show whether the Intelligence Committee can be effective in monitoring and investigating our nation’s intelligence activities or whether our work can be thwarted by those we oversee,” Feinstein said.

Sen. Patrick Leahy, D-Vt., applauded Feinstein Tuesday for speaking publicly about the dispute.

“This is not just about getting to the truth of the CIA’s shameful use of torture,” Leahy said. “This is also about the core founding principle of the separation of powers, and the future of this institution and its oversight role.”

The White House has “great confidence” in Brennan and supports the declassification of the Intelligence Committee report, said spokesman Jay Carney.