Specifically, the paper charges Italy's intelligence services with playing a lead role in fabricating and disseminating the story that Baghdad sought nuclear weapons-grade uranium in Niger. It also charges Italian authorities with remaining silent even though they believed U.S. claims that Iraq was seeking aluminum tubes for nuclear arms production were false.
The Niger and aluminum tube claims formed a cornerstone of Washington's case for war.
"It's basically a room full of mirrors, and it tends to be very, very difficult to understand whether what you are seeing is an image mirrored by someone or it's the reality. And that's the situation basically in which we are."
The Italian government, a key ally of Washington, strongly denies the allegations, as does the SISMI, Italy's military intelligence service.
Carlo Bonini, one of two reporters who helped write the stories, relied on U.S. and Italian government reports, anonymous sources and on-the-record interviews, including with SISMI chief Nicolo Pollari.
"SISMI says the Italian secret service has never thought that Saddam Hussein was capable to build an nuclear weapon," Bonini said. "If [Pollari] is saying the truth, why [did] the Italian government, on February 6, 2003, through [Prime Minister] Silvio Berlusconi, go to the parliament saying that Saddam Hussein has finally got what he needed to build a nuclear weapon?"
In a measure of the controversy sparked by the reports of "La Repubblica," senior officials including Pollari were called this month to testify before a closed-door session of the parliamentary intelligence committee in Rome.
After the publication of the reports late last month, Stephen Hadley, Bush's national security adviser, acknowledged publicly for the first time that he and other senior officials met Pollari on 9 September 2002 -- as "La Repubblica" alleged.
"There was a meeting in Washington on that date," Hadley said. "I did attend a meeting with him. It was, so far as we can tell from our records, about less than 15 minutes. It was a courtesy call. Nobody participating in that meeting or asked about that meeting has any recollection of a discussion of natural uranium, or any recollection of any documents being passed. And that's also my recollection."
Hadley was then deputy to Condoleezza Rice, the former national security adviser who is now secretary of state.
Two days after meeting with Pollari, Hadley asked the Central Intelligence Agency for clearance to use the African uranium claim in a speech by Bush. The CIA rejected the request, saying the claim was not credible enough.
But four months later, Bush, citing British intelligence, mentioned the claim during his 28 January 2003 State of the Union speech.
Hadley later assumed responsibility for letting the claim slip into Bush's speech. But that was after the UN atomic agency had declared, in March 2003, that the Niger story was bogus and based on forged documents.
So where did those documents come from?
After the parliamentary hearing, Italian lawmakers told reporters that Pollari had blamed a former SISMI agent, Rocco Martino, for disseminating the papers.
Martino himself has said he sold them to British and French intelligence.
Subsequently Pollari has said that two other SISMI agents helped Martino forge the documents. Yet as reporter Bonini said, Pollari denied to parliament that SISMI was involved in any way with the forgery or dissemination of the Niger dossier.
"Which is another quite baffling point, because on one side you say, 'We don’t have anything to do with this,'" Bonini said. "But on the other side you admit that the three guys who were involved directly in fabricating the dossier were in a way or in another, linked to the service [SISMI]."
On 4 November, the day after Pollari's appearance in parliament, the U.S. Federal Bureau of Investigation said that its probe into the Niger forgeries had concluded that they were not part "of an [Italian] effort to influence U.S. foreign policy."
But on the same day Knight-Ridder, a chain of U.S. newspapers, cited four anonymous U.S. intelligence sources who said SISMI passed reports on Iraq and Niger to the CIA station in Rome between October 2001 and March 2002.
With such a plethora of conflicting views and anonymous sources, experts say it may take a while to find the truth to the Niger story. Giovanni Gasparini is a senior fellow for defense and security studies with the Institute of Foreign Affairs in Rome. He said: "The problem is that it's the whole intelligence system that works in a way that makes it very difficult to understand what is the truth and what is not. It's basically a room full of mirrors, and it tends to be very, very difficult to understand whether what you are seeing is an image mirrored by someone or it's the reality. And that's the situation basically in which we are."
According to a 2004 Senate Intelligence Committee report, a "foreign intelligence service" provided the CIA with three reports on the alleged Iraq-Niger deal between October 2001 and October 2002.
Many believe that intelligence service is the SISMI. Gasparini, among others, has his doubts.
That same Senate committee recently agreed to look into possible misuse by the administration of intelligence during the run-up to the Iraq war. The committee may find that some roads -- if not all -- lead to Rome.