Senior US officials in the Bush administration were involved in the approval of the use of torture on so-called terror detainees by CIA employees, a US senate report has said.
The use of torture against detainees also led to the brutal mistreatment of terror suspects and prisoners in places such as Iraq's Abu Ghraib prison, the senate armed services committe report said.
"The fact is that senior officials in the US government solicited information on how to use aggressive techniques, redefined the law to create the appearance of their legality, and authorised their use against detainees," the report said on Tuesday.
The report also dismissed claims by Bush aides that abuse of detainees in US military facilities in places such as Guantanamo Bay, Iraq and Afghanistan were the "unauthorised acts of a 'few bad apples' as "simply false".
"Authorisations of aggressive interrogation techniques by senior officials resulted in abuse and conveyed the message that physical pressures and degradation were appropriate treatment for detainees in US military custody," Carl Levin, a Democratic senator and head of the committee, said in a statement.
"[The report is] a condemnation of both the Bush administration's interrogation policies and of senior administration officials who attempted to shift the blame for abuse ... to low-ranking soldiers."
The investigation into US treatment of "war on terror" detainees, exerpts of which were published in December, is likely to increase debate over US use of torture.
It also follows the release last week by the administration of Barack Obama, the US president, of several justice department memos dating from the presidency of George Bush, Obama's predecessor, which approved the CIA's use of "waterboarding", which simulates the sensation of drowning, and other methods.
The report says the Bush administration began preparing for what came to be known as "enhanced interrogation" techniques just a few months after the September 11, 2001, attacks and before the development of the memos approving such practises.
It also details warnings from experts warning that such methods was likely to yield "less reliable" results than less aggressive methods.
According to a memo obtained by the Associated Press news agency, Dennis Blair, Obama's national intelligence director, said on Tuesday that "high value information'' had been obtained in harsh interrogations approved by the Bush administration.
However, a statement issued later in the day in Blair's name said there was "no way of knowing whether the same information could have been obtained through other means".
Obama banned the use of waterboarding and other methods used under the Bush administration shortly after entering office in January, saying that the US must stick to the army's field manual guidelines on the treatment of detainees.
He also on Tuesday left open the possibility of prosecuting officials over the memos released last week.
Obama reiterated his belief that US intelligence agents and interrogators who took part in waterboarding and other interrogation methods after acting on advice from superiors who defined such practices as legal should not face prosecution.
But Obama said it was up to Eric Holder, the US attorney-general, whether to prosecute Bush-era lawyers who wrote the memos approving the tactics.
Holder said in his confirmation hearings last year that he considered waterboarding to be torture.
Obama also said that he would support a congressional investigation over the issue if it were conducted in a bipartisan manner.
"That would probably be a more sensible approach to take," he said.
In another development, Dick Cheney, the former US vice-president under Bush, criticised the decision by the Obama adminstration to release the documents.
Cheney told Fox News that the US had obtained valuable information from using such methods on so-called terror suspects following the September 11 attacks in 2001.
"One of the things that I find a little bit disturbing about this recent disclosure is they put out the legal memos, the memos that the CIA got from the Office of Legal Counsel, but they didn't put out the memos that showed the success of the effort," he told the channel on Monday.
"I know specifically of reports that I read, that I saw, that lay out what we learned through the interrogation process and what the consequences were for the country."