WASHINGTON: The head of the US Senate Intelligence Committee claimed on Tuesday that the CIA had improperly searched the panel's computers.

Senator Dianne Feinstein, a Democrat, demanded an apology in a speech on the Senate floor and also revealed that the US Justice Department had been asked to look into the matter.

The speech was the latest salvo in an escalating battle between the CIA and the Senate over an interrogation programme the CIA conducted in the early 2000s. Last week, some US Senators accused the CIA of monitoring Senate staff investigating the matter.

Senator Feinstein rejected the agency's claim that the staff had illegally obtained documents relating to this programme. She said the CIA had willingly provided the documents but later tried to remove them from the Senate facilities. This amounted to prohibiting the committee from investigating its controversial interrogation and detention programme, she said. But CIA Director John Brennan denied that the agency had done anything wrong.

He told NBC News that the CIA did not try to interfere with the congressional investigation of water-boarding and other interrogation techniques that took place during the President George W. Bush administration.

“The CIA was in no way spying on (the committee) or the Senate,” Mr Brennan said.

Senator Feinstein, however, claimed that in 2009 the CIA agreed to allow Senate staff to review documents related to this programme but in 2010 revoked access to previously accessible files had been revoked.

She said she raised the issue with the White House counsel who “recognised the severity of the situation and the grave implications” of executive branch personnel interfering with an official congressional investigation.

The matter was resolved with a renewed commitment from the White House counsel and the CIA that the agency would continue to allow Senate staff access to those documents.

Senator Feinstein rejected the CIA’s stance that Senate staff shouldnot have had access to the documents. “I reject that claim completely,” she said while accusing the spy agency of “intimidating” Congress. During her 40-minute speech on the Senate floor, the Senator claimed that the CIA's action was undermining the US constitution.

“I have grave concerns that the CIA's search may well have violated the separation of powers principles embodied in the United States Constitution, including the speech and debate clause,” she said.