WASHINGTON  The Iraqi defector whose claims that Saddam Hussein’s government had biological weapons became part of the Bush administration’s justification for the 2003 invasion of Iraq has admitted that he fabricated his story.

The defector, Rafid Ahmed Alwan al-Janabi, who was code-named “Curveball” by the Central Intelligence Agency and German intelligence officials, told the British newspaper The Guardian on Tuesday that he had concocted his tale that Iraq was hiding mobile bioweapons laboratories. He did so, he said, in hopes that his lies would lead to the eventual overthrow of the Iraqi ruler.

“I had the chance to fabricate something to topple the regime,” Mr. Janabi told the newspaper. “I and my sons are proud of that, and we are proud that we were the reason to give Iraq the margin of democracy.”

Mr. Janabi, who lives in Germany, has given several interviews in the past, but until now has always denied that he had lied to his intelligence handlers before the war in Iraq, even though his information had long been discredited.