Leading Democrats in the US have called for a criminal investigation into the CIA's destruction of two tapes showing the interrogation of al-Qaeda suspects.
Senator Kennedy expressed anger about the destruction of the tapes
The CIA says it wiped the tapes to protect the identities of its agents.
But human rights groups accuse it of destroying evidence of practices that may be tantamount to torture.
US President George W Bush has said he has "no recollection" of the existence of the tapes and he was not aware of the plan to destroy them.
Senator Dick Durbin, the second most powerful Democrat in the Senate, called on US Attorney General Michael Mukasey to investigate "whether CIA officials who destroyed these videotapes and withheld information about their existence from official proceedings violated the law".
Other Democrats expressed anger about the destruction of the tapes.
CIA 'ENHANCED INTERROGATION' TECHNIQUES
Water boarding: prisoner bound to a board with feet raised, and cellophane wrapped round his head. Water is poured onto his face and is said to produce a fear of drowning
Cold cell: prisoner made to stand naked in a cold, though not freezing, cell and doused with water
Standing: Prisoners stand for 40 hours and more, shackled to the floor
Belly slap: a hard slap to the stomach with an open hand. This is designed to be painful but not to cause injury
Source: Described to ABC News by un-named CIA agents in 2005
"The past six years, the Bush administration has run roughshod over our ideals and the rule of law," said veteran Democratic Senator Edward Kennedy.
"Now, when the new Democratic Congress is demanding answers, the administration is feverishly covering up its tracks," he said.
Carl Levin, Democratic chairman of the Senate Armed Services Committee, cast doubt on the CIA's statement that the tapes were destroyed to protect the identity of its agents.
"You'd have to burn every document at the CIA that has the identity of an agent on it under that theory," he said.
The Senate Intelligence Committee has promised a thorough investigation into the history of the making and wiping of the tapes.
President Bush continued to have confidence in CIA Director Michael Hayden, White House spokeswoman Dana Perino said.
The president "did not remember" being told of the tapes prior to Thursday, she said.
The CIA revelation has drawn criticism from civil liberties and human rights groups.
Jennifer Daskal, senior counsel with Human Rights Watch, said the wiping of the tapes was "destruction of evidence", and described the reasons given by the CIA as "disingenuous".
The American Civil Liberties Union accused the agency of showing an utter disregard for the law.
"The destruction of these tapes appears to be a part of an extensive, long-term pattern of misusing executive authority to insulate individuals from criminal prosecution for torture and abuse," an ACLU statement said.
Gen Hayden explained why the footage was destroyed in an internal memo sent to CIA employees and obtained by the Associated Press.
He said the CIA had begun taping interrogations as an internal check in 2002 and decided to delete the videos because they no longer had "intelligence value" and posed a security risk.
"Were they ever to leak, they would permit identification of your CIA colleagues who had served in the programme, exposing them and their families to retaliation from al-Qaeda and its sympathisers," he said.
The BBC's Jonathan Beale in Washington says the news is likely to trigger more questions about the interrogation techniques used by the CIA and whether they amounted to torture.
Michael Hayden wrote to all CIA employees about the tapes
According to our correspondent, those techniques are alleged to have included water-boarding, a method in which a suspect is made to feel he is drowning.
Human rights groups say that water-boarding - and other techniques allegedly used by the CIA - can be defined as torture under various international treaties to which the US is a signatory.
The Bush administration has always maintained that it does not allow the use of torture.
The tapes are thought to have shown the interrogation in 2002 of a number of terror suspects, including Abu Zubaydah, who had been a chief recruiter for the al-Qaeda network.