A top-ranking US senator on Tuesday accused the Central Intelligence Agency of illegally interfering in a congressional probe into the agency’s controversial detention and interrogation programmes during the Bush administration.

Senator Dianne Feinstein, chairwoman of the Senate Intelligence Committee, accused the CIA of removing documents from computers a congressional committee used to investigate the agency.

Ms. Feinstein said she wanted to “set the record straight” regarding reports about CIA intrusion into Senate investigators’ computers.

At issue are the interrogation methods of suspected terrorists that bordered on torture — and which were stopped and banned when President Barack Obama took office in 2009.

The Senate finished its report on the practices in 2012 and sent it to the CIA for review before declassification.

The CIA responded in 2013 and opposed declassification of parts of the report that dealt with the very documents that congressional researchers found had been illegally removed.

The White House on Tuesday supported Ms. Feinstein’s call for declassification of the report on the programme, but said only with the agency’s approval.

Speaking at the Council on Foreign Relations think tank, CIA director John Brennan worried out loud that declassification would undermine the need to protect individuals who were involved. He insisted that there had to be “a balanced and even—handed and accurate portrayal of that programme.” The Department of Justice has started investigating possible wrongdoing in the committee’s writing of the review at the request of the independent inspector general for the CIA.

“If there was any inappropriate actions that were taken related to that review either by CIA or by the (committee) staff, I’ll be the first one to say we need to get to the bottom of this,” Mr. Brennan said.

Ms. Feinstein said she had “grave concerns” about the CIA’s actions during the probe, which may have “undermined the constitutional framework” that guarantees congressional oversight of intelligence activities and other government activities.

The Senate committee had an agreement with the CIA that called for the agency to provide the investigative staff with a stand—alone computer system at a secure CIA location.

“On two occasions CIA personnel electronically removed committee access to CIA documents after providing them to the committee,” Ms. Feinstein charged.

“In short, this was the exact sort of CIA interference in our investigation that we sought to avoid at the outset.” Ms. Feinstein also said that the CIA had later conducted unauthorized searches on the CIA—supplied computers.

Ms. Feinstein said that the CIA initially blamed contractors for the missing documents, then said the White House had ordered the removals, but the White House denied giving such an order.

Then came allegations that “the committee staff had somehow obtained the document through unauthorized or criminal means, perhaps to include hacking into the CIA’s computer network,” she noted.

Ms. Feinstein said there was “no legitimate reason to allege to the Justice Department that Senate staff may have committed a crime.” “I view the acting counsel general’s referral as a potential effort to intimidate this staff, and I am not taking this lightly,” she said.

The committee’s 6,300—page report on the interrogation programme remains classified.

“If the Senate can declassify this report, we will be able to ensure that an un—American, brutal programme of detention and interrogation will never again be considered or permitted,” she said.

Resolution of the issue will show whether the committee can be effective “or whether our work can be thwarted by those we oversee,” Ms. Feinstein concluded.

The American Civil Liberties Union praised Ms. Feinstein for her “forceful, necessary, and historic defense of the constitutional principle of separation of powers.” “Public release of the Senate torture report will be the next step to reining in a CIA that has tortured, destroyed evidence, spied on Congress, and lied to the American people,” said Christopher Anders, senior legislative counsel with the ACLU.

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