Colin Powell, who presented the case for military action against Saddam Hussein in the United Nations in 2003, has told a BBC interview he was now "deeply disappointed" in information received from intelligence agencies.
He said he was particularly upset that the agencies had failed to convey doubts they had about some of the sourcing of the information.
Mr Powell said: "Those doubts never surfaced to us."
His comments follows US President George W. Bush's speech last week in which he accepted responsibility for going to war on intelligence, much of which he conceded, turned out to be "wrong".