WASHINGTON - A former FBI interrogator who questioned al Qaeda prisoners testified yesterday that the Bush administration falsely boasted of success from extreme techniques like waterboarding, when those methods were slow, unreliable and made an important witness stop talking.

Ali Soufan, testifying to a Senate panel behind a screen to hide his identity, said his team's non-threatening interrogation approach elicited crucial information from al Qaeda operative, Abu Zubaydah, including intelligence on "dirty bomb" terrorist Jose Padilla.

Soufan said his team had to step aside when CIA contractors took over. They began using harsh methods that caused Zubaydah to "shut down," Soufan said, and his team had to be recalled the get the prisoner talking again.

Soufan testified before a Senate Judiciary subcommittee holding the first hearing on extreme-interrogation methods since the Obama administration last month released Bush administration legal opinions authorizing them.

Memos by the Bush Justice Department contended that waterboarding - a form of simulated drowning - as well as sleep deprivation and other extreme techniques were legal under U.S. and international law, but Democrats said they amounted to torture.

President Obama has said he wanted to avoid partisan hearings over the interrogations, but the hearing turned partisan in its opening seconds.

Subcommittee Chairman Sen. Sheldon Whitehouse, D-R.I., promised at the outset to unravel "our country's descent into torture" and vowed to expose "a bodyguard of lies" by the Bush administration.

Sen. Lindsey Graham, R-S.C., asked whether "we would have this hearing if we were attacked this afternoon."

Graham called the hearing a "political stunt" and said Democrats were trying to judge officials who - soon after the 9/11 terror attacks - "woke up one morning like most Americans and said, 'Oh, my God, what's coming next?' "

He also joined in Republican criticism that members of Congress, including House Speaker Nancy Pelosi, had been briefed on the interrogation program and raised no protest at the time. *