Pressure to prosecute senior figures in the Bush Administration intensified yesterday after a Senate report concluded the high-level approval of harsh CIA interrogation techniques "set the tone" for subsequent abuse of detainees in military prisons.

The publication of the Armed Services Committee inquiry into the treatment of prisoners by the US military was accompanied by fresh calls for a special prosecutor, as well as the creation of a independent commission, by which legal advisers - or even George Bush and Dick Cheney themselves - may be held to account for their decisions.

The report said officials began preparing for "enhanced interrogation" methods shortly after the September 11, 2001 attacks and eight months before memos authorising their use were written.

Committee chairman, the Democratic Senator Carl Levin, said that claims by Bush administration policy-makers that "detainee abuses could be chalked up to the unauthorised acts of a 'few bad apples,' were simply false." He attacked efforts to "shift the blame for abuse" at prisons such as Abu Ghraib "to low ranking soldiers".

Mr Bush's decision to abandon Geneva Convention protections and the legal advice authorising the CIA's use of techniques led to "an erosion in standards dictating that detainees be treated humanely," said the report. The message filtered down to troops running sites in Iraq, Afghanistan and elsewhere "that physical pressures and degradation were appropriate treatment for detainees in US military custody".

For instance, Jonathan Fredman, chief counsel to the CIA's Counter-terrorist centre, told a meeting of Guantanamo personnel that laws banning torture were "vaguely written" and "subject to perception". According to minutes obtained by the committee, he added: "If the detainee dies you're doing it wrong".

When President Obama last week declassified top secret memos on the interrogation methods he expressed the hope it would help close "a dark and painful chapter" in American history so that he can focus efforts on his vast agenda both at home and abroad.

But this week, following a series of confused or contradictory briefings and ill-advised statements by senior White House officials, such disclosures appeared only to have fuelled demands for an ever more forensic prosecutorial examination of his predecessor's Administration.

Mr Obama has already conceded that lawyers who drafted the memos may face criminal sanction. Reports yesterday suggested the Justice Department had complained that a comment from White House chief of staff Rahm Emanuel at the weekend, dismissing calls for the lawyers to be prosecuted, amounted to political interference in a judicial process.

In another instance of uneasy handling of the dispute, Dennis Blair, Director of National Intelligence, appeared to acknowledge in a memo to staff that the contested interrogation techniques had yielded "high-value information". Significantly, this apparent endorsement of claims from former vice-president Dick Cheney was omitted from a public version of his assessment.

Although Mr Obama has consistently stated that it would be wrong to pursue CIA interrogators who obeyed legal guidance, there is a growing clamour from human rights groups for court action. One possible route is through Europe where activists in both Spain and Germany are already pushing for the prosecution of Bush Administration officials.

Mr Levin effectively called for the appointment of a special prosecutor by saying it was necessary for a senior judicial figure "to recommend what steps, if any, should be taken to establish accountability of high-level officials".

The President has - reluctantly - begun to open the door for the establishment of an independent inquiry by indicating that "if and when" Congress establishes such a body, he would prefer it be modelled on the 9/11 Commission by looking forward to what lessons need to be learned.

Others, including Senate Judiciary Committee chairman Patrick Leahy, have demanded a "Truth and Reconciliation Commission" to probe deep into the recent past.

The Armed Services committee report details how policy-makers ignored repeated warnings from military experts that harsh questioning was likely to yield "less reliable" intelligence results than less aggressive approaches.

One July 2002 memo from the agency that ran a training programme for military personnel to resist interrogation when captured, stated: "A subject in extreme pain may provide an answer, any answer, or many answers in order to get the pain to stop."

The report, however, also quoted US Army psychiatrist Major Paul Burney saying: "A large part of the time we were focused on trying to establish a link between Al-Qaeda and Iraq. The more frustrated people got in not being able to establish this link... there was more and more pressure to resort to measures that might produce more immediate results."

Times Recommends

• Please help: maimed children of war want their lives back
• Cabal seizes diamond riches to buy power
• White House gatecrashers got to the president