Foiled UK terror plots were falsely held up by America's CIA as proof that its "brutal" torture tactics had saved lives, a US intelligence watchdog has said.
In a long-awaited report, the Senate Intelligence Committee said the interrogation of detainees in the wake of the 9/11 attacks were "far worse" than the CIA had portrayed to the US Government.
Waterboarding methods had deteriorated to "a series of near drownings" and Agency staff subjected detainees to "rectal rehydration" and other painful procedures that were never approved, the report said.
The CIA justified its use of so-called enhanced interrogation techniques with "inaccurate claims of their effectiveness" including examples of thwarted UK plots such as a plan by 9/11 mastermind Khalid Sheikh Mohammed to hijack planes and attack Heathrow airport and Canary Wharf.
The capture of al Qaida UK operative Dhiren Barot and the arrest of British would-be shoe-bomber Saajid Badat were also among the Agency's eight most f requently cited examples of how using torture methods "saved lives".
Prime Minister David Cameron said some activities after the 9/11 attacks had been "wrong" but added he was "confident the issue has been dealt with from a British perspective".
And the CIA remained defiant with Director John Brennan insisting the controversial methods did produce intelligence that helped thwart attack plans, capture terrorists and save lives.
In the report, which is a 480-page executive summary of the more than 6,000-page original, chair of the Committee Senator Dianne Feinstein said: The major lesson of this report is that regardless of the pressures and the need to act, the Intelligence Community's actions must always reflect who we are as a nation, and adhere to our laws and standards.
"It is precisely at these times of national crisis that our government must be guided by the lessons of our history and subject decisions to internal and external review.
"Instead, CIA personnel, aided by two outside contractors, decided to initiate a program of indefinite secret detention and the use of brutal interrogation techniques in violation of US law, treaty obligations, and our values."
American embassies, military units and other US interests were put on high alert for possible security threats ahead of release of the report, which follows a five-year investigation by the Committee.
Among torture methods used by the CIA across its secret prison network were the use of insects placed in a confinement box, sleep deprivation and the now-notorious practice of waterboarding.
Other techniques included the attention grasp, which involves grasping an individual with both hands on each side of a collar opening; walling, which is when an individual is pushed against a wall quickly; and stress positions.
The Committee concluded that the CIA's use of interrogation techniques was not an effective means of acquiring intelligence or gaining co-operation from detainees. It also found that the CIA's justification for the use of these torture methods "rested on inaccurate claims of their effectiveness".
Among cases cited were a number of UK-linked plots or arrests, which the CIA said were assisted by its interrogation programme.
One is the case of convicted terrorist Barot, who was sentenced at Woolwich Crown Court in 2006 to life, with a minimum term of 30 years, for planning to plant radioactive, chemical or toxic gas bombs and pack limousines with nails and explosives in the UK and America.
Over a number of years, the CIA used the capture of the north London schoolboy and thwarting of his plots as evidence for the "effectiveness" of enhanced interrogation techniques.
But the report concluded their claims were "inaccurate".
It said: "The operation that resulted in... Dhiren Barot's arrest, and the thwarting of his plotting, resulted from the investigative activities of UK government authorities."
The CIA also claimed that the smashing of a plot hatched by suspected 9/11 mastermind Mohammed to fly hijacked planes into Heathrow Airport and Canary Wharf as evidence for the "effectiveness" of their interrogation tactics.
After the Twin Towers atrocity, Mohammed was said to have "sought to target the United Kingdom using hijacked aircraft and surmised that Heathrow Airport and a building in Canary Wharf, a major business district in London, were powerful economic symbols".
It went on: "The initial plan was for al Qaida operatives to hijack multiple airplanes departing Heathrow Airport, turn them around, and crash them into the airport itself.
"Security was assessed to be too tight at Heathrow Airport and the plan was altered to focus on aircrafts departing from mainly Eastern European airports to conduct attacks against Heathrow Airport. Al-Qaida was unable to locate pilots to conduct these attacks."
The purported disruption of a plot against Heathrow and Canary Wharf was one of the eight most frequently cited examples used by the CIA to justify its interrogation activities, but again the Committee said the claims were "inaccurate".
It said: "The CIA represented that its enhanced interrogation techniques were effective and produced critical, otherwise unavailable intelligence, which thwarted plots and saved lives.
"Over a period of years, the CIA provided the identification and thwarting of the Heathrow Airport plot as evidence for the effectiveness of the CIA's enhanced interrogation techniques.
"These representations were inaccurate. A review of records indicates that the Heathrow Airport and Canary Wharf plotting had not progressed beyond the initial planning stages when the operation was fully disrupted."
Over a period of years, the CIA also flagged the identification, discovery, capture and arrest of Badat to support its controversial practices.
Badat was jailed in 2005 after he admitted plotting to explode a shoebomb on a transatlantic flight in December 2001 at the same time as fellow shoebomber Richard Reid, but changed his mind and decided not to go through with it.
Again, the CIA representations were inaccurate and the report added: "UK domestic investigative efforts, reporting from foreign intelligence services, international law enforcement efforts, and US military reporting resulted in the identification and arrest of Saajid Badat."
Reacting to the report, CIA director John Brennan said the techniques were authorised by the Bush administration.
Mr Brennan said the Agency had "made mistakes" and acknowledged that the detention and interrogation programmes "had shortcomings".
However, he said the CIA disagreed with the Committee on some key points, adding its own review suggests use of the torture methods did produce intelligence that helped thwart attack plans, capture terrorists and save lives.
"The intelligence gained from the programme was critical to our understanding of al Qaida and continues to inform our counter-terrorism efforts to this day," he said.
British human rights groups called for a judge-led inquiry into the UK's involvement in the scandal.
Director of Liberty Shami Chakrabarti said: "The breadth and brutality of CIA torture is laid bare - can our own authorities keep averting their eyes?
"Still no sign of a judge-led inquiry into UK involvement in this shameful scandal - instead the Government's new Bill furnishes the agencies with more powers to leave Britons vulnerable to torture abroad."
Amnesty International Americas director Erika Guevara Rosas said: " This report provides yet more damning detail of some of the human rights violations that were authorised by the highest authorities in the USA after 9/11.
"The declassified information contained in the summary, while limited, are a reminder to the world of the utter failure of the USA to end the impunity enjoyed by those who authorised and used torture and other ill-treatment.
"This is a wake-up call to the USA, they must disclose the full truth about the human rights violations, hold perpetrators accountable and ensure justice for the victims. This is not a policy nicety, it is a requirement under international law."
Speaking after talks with the Turkish prime minister in Ankara, the Prime Minister said: "Let's be clear: torture is wrong; torture is always wrong."
He added: "In Britain we have had the Gibson Inquiry and that inquiry has now produced a series of questions that the Intelligence and Security Committee will look at.
"But I am satisfied that our system is dealing with all these issues and I, as Prime Minister, have issued guidance to all of our agents and others working around the world about how they have to handle these issues in future."