The officials on Friday said the UN mission exceeded its authority in accusing the government of negligence.
The report from a UN fact-finding mission was sharply critical of Syria and its allied Lebanese government, saying there was evidence Syria's president threatened al-Hariri with physical harm.
The report said the Beirut government showed a lack of commitment to finding out who killed al-Hariri, bungling and outright manipulating the investigation.
Many Lebanese blame Syria and the Syrian-backed Lebanese government for the slaying of al-Hariri - an opponent of Syrian domination - in a 14 February bomb blast. Damascus and Beirut deny any role in the killing.
Lebanese Foreign Minister Mahmud Hamud said the UN fact-finding team, whose report was released on Thursday, had gone beyond its mandate.
Lahud (L) indicated acceptance of
an international inquiry
"The [UN] mission had no authority to allow it to reach these conclusions," he said. "We see this as infringement on the role of the Lebanese government."
Still, he insisted that the government "welcomes all means" to find the truth about the killing.
Lebanese President Emile Lahud urged UN Secretary-General Kofi Annan late on Thursday to do "what is necessary" to uncover the truth, signalling Lebanon's acceptance of an international inquiry it had been rejecting since the bombing.
The UN report said "it is clear that the assassination took place in a political and security context marked by an acute polarisation around the Syrian influence in Lebanon".
Hamud rejected this, saying tensions were caused by the United Nations' calling for Syria to withdraw its troops from Lebanon in Resolution 1559.
Tensions were caused by a demand
for Syrian withdrawal, said Hamud
"We say that tension began when signals started coming from abroad that a resolution was to be issued by the Security Council - it later became 1559 - this resolution pushed the atmosphere toward political polarisation," Hamud said.
Justice Minister Adnan Adum said the UN report was not a legal opinion and rejected claims of evidence tampering. "We consider it a technical, security document and it cannot be considered a legal and judicial document," he said.
But Interior Minister Sulayman Franjiyah acknowledged "flaws" in the security system as the report noted.
Syrian military intelligence shares responsibility with Lebanese security forces for failing to provide "security, protection, law and order" in Lebanon, the report said.
"We consider it a technical, security document and it cannot be considered a legal and judicial document"
Lebanese justice minister
But Hamud countered: "This is far from reality."
The report said there was a "distinct lack of commitment" by the authorities to investigate the crime, and 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.
Adum denied that car parts were placed in the crater.
"The proof is that the wreckage of the car was found in the sea near the site and was retrieved by divers who were international experts," he said.
The UN report said the blast was caused by a surface explosion of about one tonne of TNT. The government has contended that a car bomber struck al-Hariri's motorcade.