WASHINGTON (AP) — The head of the Senate Intelligence Committee declared on Tuesday that the CIA interfered with and then tried to intimidate a congressional investigation into the agency's possible use of torture in terror probes during the Bush administration.

The CIA clandestinely removed documents and searched a computer network set up for lawmakers, said Sen. Dianne Feinstein in a long and biting speech on the Senate floor. In an escalating dispute with an agency she has long supported, she said the CIA may well have violated criminal laws and the U.S. Constitution.

The dispute between the CIA and senators, which has been going on privately for more than five years, exploded into a public clash as Feinstein offered a detailed account of the Senate's secretive dealings with the CIA in an investigation of post-Sept. 11 interrogation and detention practices.

More broadly, all U.S. spy agencies have drawn intense scrutiny since revelations last summer about surveillance of Americans by the National Security Agency. The Obama administration has struggled to rebuild public trust since former analyst Edward Snowden made the disclosures. Feinstein has been one of the intelligence community's most ardent advocates, arguing that the wide surveillance of people's electronic and telephone communications was a necessary counterterrorism tool.

At odds on major contentions, both sides have involved the Justice Department. The CIA's inspector general, David Buckley, has referred the matter to Justice, and the CIA's acting counsel responded by filing a criminal report about the intelligence committee staff.

"I am not taking it lightly," Feinstein said of the tit-for-tat investigations. "I view the acting counsel general's referral as a potential effort to intimidate this staff" in the interrogation investigation.

In the current matter, CIA Director John Brennan rejected Feinstein's accusations, insisting that the agency was not trying to thwart the committee's work and denying that it had been spying on the panel or the Senate. He said the appropriate authorities would look at the matter further and "I defer to them to determine whether or not there was any violation of law or principle."

Brennan said if he did "something wrong, I would go to the president and he would be the one to ask me to stay or go."

Both Feinstein and the CIA acknowledge they examined documents that were part of the investigation but insisted that they acted appropriately in following an agreement worked out between her committee and then-CIA Director Leon Panetta in 2009.

But Feinstein and the CIA also have accused each other's staffs of improper behavior. She said she had "grave concerns that the CIA's search may well have violated the separation of powers principles embodied in the United States Constitution," as well as the Fourth Amendment that prohibits unreasonable searches and seizures.

She said she has sought an explanation and an apology from the CIA. Neither has been forthcoming.

Feinstein received a standing ovation from her Democratic colleagues at a closed-party lunch on Tuesday. Several Republicans also expressed their concerns, but the Intelligence Committee's top Republican, Saxby Chambliss of Georgia, wasn't one of them.

He indicated he disagreed with her on the dispute, without providing specifics. He called for a study "on what happened so people can find out what the facts are."

"We're going to continue to deal with this internally," he told reporters.

Other senators said the dispute had a chilling effect on congressional oversight.

"Heads should roll, people should go to jail if it's true," said Sen. Lindsey Graham. "If it is, the legislative branch should declare war on the CIA."

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Associated Press writers Bradley Klapper, Stephen Braun and Kimberly Dozier contributed to this report.