The German intelligence officials responsible for one of the most important informants on Saddam Hussein's suspected weapons of mass destruction say that the Bush administration and the CIA repeatedly exaggerated his claims during the run-up to the war in Iraq.

Five senior officials from Germany's Federal Intelligence Service, or BND, said in interviews with The Times that they warned U.S. intelligence authorities that the source, an Iraqi defector code-named Curveball, never claimed to produce germ weapons and never saw anyone else do so.

According to the Germans, President Bush mischaracterized Curveball's information when he warned before the war that Iraq had at least seven mobile factories brewing biological poisons. Then-Secretary of State Colin L. Powell also misstated Curveball's accounts in his prewar presentation to the United Nations on Feb. 5, 2003, the Germans said.

Curveball's German handlers for the last six years said his information was often vague, mostly secondhand and impossible to confirm.

"This was not substantial evidence," said a senior German intelligence official. "We made clear we could not verify the things he said."

The German authorities, speaking about the case for the first time, also said that their informant suffered from emotional and mental problems. "He is not a stable, psychologically stable guy," said a BND official who supervised the case. "He is not a completely normal person," agreed a BND analyst.

Curveball was the chief source of inaccurate prewar U.S. accusations that Baghdad had biological weapons, a commission appointed by Bush reported this year. The commission did not interview Curveball, who still insists his story was true, or the German officials who handled his case.

The German account emerges as the White House is lashing out at domestic critics, particularly Senate Democrats, over allegations the administration manipulated intelligence to go to war. Last week, Vice President Dick Cheney called such claims reprehensible and pernicious.

In Congress, the Senate Select Committee on Intelligence is resuming its long-stalled investigation of the administration's use of prewar intelligence. Committee members said last week that the Curveball case would be a key part of their review. House Democrats are calling for a similar inquiry.

An investigation by The Times based on interviews since May with about 30 current and former intelligence officials in the U.S., Germany, England, Iraq and the United Nations, as well as other experts, shows that U.S. bungling in the Curveball case was worse than official reports have disclosed.

The White House, for example, ignored evidence gathered by United Nations weapons inspectors shortly before the war that disproved Curveball's account. Bush and his aides issued increasingly dire warnings about Iraq's biological weapons before the war even though intelligence from Curveball had not changed in two years.

At the Central Intelligence Agency, officials embraced Curveball's account even though they could not confirm it or interview him until a year after the invasion. They ignored multiple warnings about his reliability before the war, punished in-house critics who provided proof that he had lied and refused to admit error until May 2004, 14 months after the invasion.

After the CIA vouched for Curveball's accounts, Bush declared in his 2003 State of the Union speech that Iraq had "mobile biological weapons labs" designed to produce "germ warfare agents." Bush cited the mobile germ factories in at least four prewar speeches and statements, and other world leaders repeated the charge.

Powell also highlighted Curveball's "eyewitness" account when he warned the United Nations Security Council on the eve of war that Iraq's mobile labs could brew enough weapons-grade microbes "in a single month to kill thousands upon thousands of people."

The senior BND officer who supervised Curveball's case said he was aghast when he watched Powell misstate Curveball's claims as a justification for war.

"We were shocked," the official said. "Mein Gott! We had always told them it was not proven.... It was not hard intelligence."

In a telephone interview, Powell said that George J. Tenet, then the director of central intelligence, and his top deputies personally assured him before his U.N. speech that U.S. intelligence on the mobile labs was "solid." Since then, Powell said, the case "has totally blown up in our faces."

Many officials interviewed for this report, including the German intelligence officers, spoke on the condition they not be identified because they were bound by secrecy agreements, were not authorized to speak to the news media or because the case involved classified sources and methods.

Curveball lives under an assumed name in southern Germany. The BND has given him a furnished apartment, language lessons and a stipend generous enough that he does not need to work. His wife has emigrated from Iraq, and they have an infant daughter.