Hassam told state television that he had testified against Syrian officials under duress.

Meanwhile, Syria demanded Monday, November 28, that the Mehlis report be revised after state television broadcast the apparent recanting of a witness.

Ibrahim Darraji, who heads Syria's own separate investigation into the killing, said the new testimony from Kurdish former intelligence agent Hassam Taher Hassam spelled the collapse of last month's findings by Mehlis which prompted a Security Council resolution against Damascus.

"From a legal point of view, the Mehlis report has collapsed," Darraji told reporters at a joint news conference with the purported witness in Damascus.

"It was based on the testimony of two key witnesses -- Mohammed Zuheir -- who is now jailed in France and Hassam," he said, standing alongside Hassam.

"The ball is now in the Mehlis commission's court -- they based their findings on the statements of one person and he has now set the record straight."

In the lengthy TV interview, Hassam told state television that he had testified against the brother and brother-in-law of President Bashar Al-Assad only under duress.

"Maher Al-Assad and Assef Shawkat were the main officials in their sights ... they asked me to speak out against them and I said that they were the ones who ordered the murder," he said.

He said he regretted making what he described as the "entirely false" statements that he had given.

The slain premier's son and heir, Saad, now leader of the largest bloc in the Lebanese parliament, had offered him around one million dollars, he alleged.

Hariri dismissed the accusation out of hand, describing it as a "desperate attempt to derail the inquiry" of the United Nations into his father's murder.

“Everything that this person has said is lies," said a statement released by his office in Beirut.

"We'll let an independent investigator, Mr Mehlis, make the decisions about what is credible and what is not credible," said McCormack.

A statement from the UN commission confirmed that Hassam had testified before it but added that he had volunteered his testimony and had even expressed fear about the repercussions from the Syrian authorities.

"Hassam first approached the UN International Independent Investigation Commission at the end of June 2005 and identified himself as a former Syrian intelligence officer in Lebanon," the statement said.

"In his witness statement signed and dated September 1, 2005, Mr Hassam stated: 'I am here voluntarily to give a statement to the UNIIIC. I have not been threatened or forced to come here, nor have I been offered any promises or incentives to do so.

"'I understand that by giving knowingly false information in this witness statement I may commit a crime against the laws of the Republic of Lebanon,'" the statement quoted him as saying.

The commission insisted it had "never offered or provided" any incentive for testimony and added that, according to Hassam's own statements, it was the Syrian authorities that he was afraid of.

"On several occasions Mr Hassam expressed fear to UNIIIC that he and his family could be harmed by Syrian security elements," its statement said.

The United States declined comment Monday on Syria's call to revise the UN report.

But State Department spokesman Sean McCormack said: "We'll let an independent investigator, Mr Mehlis, make the decisions about what is credible and what is not credible and what should be included in his report."