Former directors of the CIA have poured scorn on the Senate report which has revealed the brutal methods employed by the agency on terror suspects in the wake of the 9/11 attack.

Six former CIA chiefs said the 525-page condensed summary of the 6,000-page review is biased. they also argue the methods employed to extract information from prisoners directly resulted in saving "thousands of lives".

The directors submitted a jointly written a 2,500-word rebuttal in the Wall Street Journal shortly after the summary of the torture report was made public.

The six former CIA chiefs are: George J Tenet, Porter J Goss and Michael V Hayden (a retired Air Force general), and former CIA deputy directors John E McLaughlin, Albert M Calland (a retired Navy vice admiral) and Stephen R Kappes.

"A powerful example of the interrogation program's importance is the information obtained from Abu Zubaydah, a senior al Qaeda operative, and from Khalid Sheik Muhammad, known as KSM, the 9/11 mastermind. We are convinced that both would not have talked absent the interrogation program," the directors wrote.

Muhammad is said to have undergone waterboarding 183 times while he was in detention.

In the report, formulated by the Democrats on the Senate Intelligence Committee, none of the current or former CIA officials were interviewed.

The directors went on to argue that the release of the report has done long-lasting damage to the US and the CIA, as foreign agencies would no longer be willing to cooperate with the US agency as they used to.

Their written rebuttal said the committee "cherry-picked" their information from the six million pages of data, ignoring vital details in order to build the argument in a biased fashion.

The former CIA chiefs said: "We can only conclude that the committee members or staff did not want to risk having to deal with data that did not fit their construct. Which is another reason why the study is so flawed.

"What went on in preparing the report is clear: The staff picked up the signal at the outset that this study was to have a certain outcome, especially with respect to the question of whether the interrogation program produced intelligence that helped stop terrorists."

The declassification of the report, with its detailing of extreme interrogation techniques used by the CIA, has sent shock waves across the political and intelligence community.