The Government is facing mounting cross-party calls for a new judicial inquiry into allegations of British involvement in the torture of terror suspects following the exposure of brutal CIA interrogation methods.
Responsibility for probing claims surrounding the treatment of detainees was handed to parliament's intelligence and security committee (ISC) after police investigations forced the halt last year of a judge-led process.
ISC chairman Sir Malcolm Rifkind, a former Tory Party minister, insisted it would look into the matter "without fear or favour", take advantage of new freedoms to demand evidence and call witnesses - probably including ex-prime minister Tony Blair.
He also called on the White House to disclose to the committee what the UK Government and its intelligence agencies had covered up in last week's damning report by the US Senate Intelligence Committee into the CIA's use of torture.
Downing Street insists all redactions were made for reasons of national security, but the former foreign secretary said it was important to establish that there had not been a move simply to hide embarrassing revelations.
Senior Tory colleagues, however, were among those casting fresh doubt on the committee's ability to command confidence that it would fully expose the UK's role in extraordinary rendition and other activities.
Ex-shadow home secretary David Davis said: "One must understand the sheer weight of pressure that comes from the establishment to try and stop this sort of stuff coming out so I think this needs to be a judicial inquiry.
"I used to work for Malcolm Rifkind, I am a big fan of his, but... I think it has to be completely independently established."
Former cabinet minister Andrew Mitchell said it should be placed in the hands of a "judge who has had and has no connection whatsoever with the British security services".
The first detainee inquiry - led by Sir Peter Gibson - found that Britain "may have become inappropriately" involved in some cases of rendition and identified 27 areas that needed further investigation before it was axed.