But it warned that even an international investigation would be futile if the current commanders of the security forces in Lebanon remain in their posts, charging them with dereliction of duty in connection with Hariri's murder.

The report pointed a finger at Syria although stopped short of openly accusing the Assad regime of involvement in the killing, noting, instead, that Damascus was behind the political tension and weak security that led to Hariri's death with 19 other people, including six bodyguards.

"The government of Syria bears primary responsibility for the political tension that preceded the assassination," said the report from a fact-finding mission led by deputy Irish police commissioner Peter Fitzgerald, which spent a month in Beirut probing the murder.

"Clearly, Mr. Hariri's assassination took place on the backdrop of his power struggle with Syria, regardless of who carried out the assassination and with what aim," the report said.

It said the blast which shredded Hariri's motorcade as it drove by a beachside near the St. George bomb-scarred hotel was probably caused by a car-bomb rigged with 1,000 kilograms (2,200 pounds) of TNT.

"It is clear that the assassination took place in a political and security context marked by an acute polarization around the Syrian influence in Lebanon, and a failure of the Lebanese state to provide adequate protection," it said.

"There was a distinct lack of commitment on the part of the Lebanese authorities to investigate the crime effectively," it said, claiming there may have even been illegal manipulation of some evidence.

"The manner in which this element of the investigation was carried out displays at least gross negligence, possibly accompanied by criminal actions for which those responsible should be made accountable," it said.

Lebanese security services need new leadership and the proposed international probe to uncover Hariri's killers could fail if the same security bosses remained in place, the report said.

Opposition leaders in Lebanon are demanding the ouster of State Prosecutor Adnan Addoum plus the commanding generals of the nation's main security services, blaming them outright for Hariri's tragic death. They were also accused of manufacturing alibis and inventing scapegoats to absolve Syria from guilt.

In addition to the "distinct lack of commitment," the report said the Lebanese probe was not carried out "in accordance with acceptable international standards."

It detailed a host of flaws, including the disappearance of crucial evidence and tampering with the scene of the blast. Parts of a pickup truck were brought to the scene, placed in the crater and photographed as evidence, it said.

The report said investigative judges in Beirut had no control over the probe and even faulted police for not turning off a water main that flooded the blast crater and washed away vital evidence.

Studying the aftermath of the bombing, Fitzgerald's team also cast serious doubts on the legitimacy of a suspect in the bombing, a Palestinian named Ahmed Abu Adas, and a group that claimed responsibility, the little-known Support and Jihad in Syria and Lebanon.

Abu Adas did not possibly possess the skill, the equipment and the expertise to stage such an assassination operation, the report said.

Fitzgerald also faulted Syria for interfering in the governing of Lebanon "in a heavy-handed and inflexible manner." He said his investigators also received testimony that Syrian President Bashar Assad had threatened Hariri and leading opposition figure Walid Jumblat with physical harm.(AP-AFP)