Have I got a spy story for you.

It takes place just before the Iraq war. It reads like a thriller, except you can’t believe the spooks in the story could be so clumsy. The most hair-raising chapter tells the tale of a defector named Curveball, who duped the United States into believing that Iraq had mobile germ-warfare labs.

The saddest part of the tale is that it’s all true.

I refer to a recent report by the presidential commission that has been examining the ability of America’s spy agencies to find foreign weapons of mass destruction. Read it online (www.wmd.gov/report) and head straight for Chapter One, the case study on Iraq, which should make your blood boil. It states that our intel agencies’ prewar take on Iraq’s weapons of mass destruction was “dead wrong.”

The data on Saddam Hussein’s supposed nuclear, chemical and biological weapons programs – data cited repeatedly by President Bush and other top officials – were “either worthless or misleading” and were “riddled with errors.”

Worse, there was a mind-set that put forward hypotheses on WMD – then refused to consider evidence that challenged preconceived conclusions. The process was “driven by assumptions” with “inadequate validation and vetting of dubious intelligence sources.” Skeptics who tried to question flimsy evidence on key weapons issues were slapped down by senior CIA or Defense Intelligence Agency officials.

Case in point: the question of whether Hussein was reconstituting his nuclear program. This claim relied heavily on a report that Iraq was trying to buy black-market aluminum tubes to make centrifuges that would enrich uranium. But the CIA failed to get proper technical analysis, which would have shown the tubes could not do the job.

And then there is the case of Iraq’s germ-war labs on wheels. A graphic description of these shockers was the centerpiece of Secretary of State Colin Powell’s speech to the United Nations on Feb. 5, 2003. It was based almost entirely on evidence from a single source – Curveball. The only problem: Curveball was a liar.

An Iraqi defector angling for a U.S. green card, Curveball was also the brother of a top aide to Ahmed Chalabi, the Pentagon’s favorite Iraqi exile. Coincidentally, a source who corroborated Curveball’s story was provided to the Pentagon by Chalabi’s Iraqi National Congress. This source was also a fraud.

No one from the CIA ever met Curveball; he was handled by German intelligence. The one Defense Department official who did speak to Curveball described the defector as “hung over” and unreliable.

Yet as serious doubts began to mount about Curveball’s motives, no one on high wanted to listen. The scenario he delivered was too juicy.

On the eve of Powell’s speech, a senior intel official called CIA Director George Tenet to warn that Curveball’s evidence was dicey.

“Mr. Tenet replied with words to the effect of yeah, yeah’ and that he was exhausted,” according to testimony in the report. Tenet, of course, cannot recall the conversation.

The fabricated story of the germ labs remained the centerpiece of Powell’s speech.

The Curveball saga is a crucial read for the following reason: It leaves a reader with the sick but inevitable feeling that it’s bound to happen again.

Despite its frank detail, this commission’s report – like the others on intelligence failures in Iraq – has pulled its punches. It blames the intel community for poor analysis, but it lets the political appointees off the hook.

The commission states that not one intelligence analyst blamed political pressure for forcing him or her to skew or alter a report.

“That said,” the commissioners add, “it is hard to deny the conclusion that intelligence analysts worked in an environment that did not encourage skepticism about the conventional wisdom.”

No kidding! In an environment where, according to news reports, CIA analysts felt pressured by Vice President Cheney, where the Pentagon set up an Office of Special Plans to do an end run around the CIA, why would we not expect pressure to corroborate White House beliefs on WMD?

Last year, the Senate Intelligence Committee’s report on America’s prewar intelligence described how such pressure affected the Curveball case. When the one intel agent who had met Curveball tried to warn the CIA about him, a senior official replied (by e-mail): “Let’s keep in mind the fact that this war’s going to happen regardless of what Curveball said or didn’t say, and the powers that be probably aren’t interested in whether Curveball knows what he is talking about.”

That’s pretty scary when you consider that the powers that be must decide how to handle other nuclear powers or wanna-bes. And that the commission report says our intelligence agencies know “disturbingly little” about the capabilities and intentions of Iran and North Korea.

Curveball redux, here we come?

Trudy Rubin is a columnist and editorial-board member for the Philadelphia Inquirer.