The United Nations failed to respond to warnings and protect civilians during the final stages of the country's bloody civil war, according to an internal UN report leaked to the BBC.
The damning report - compiled by a panel headed by former senior UN official Charles Petrie - said many senior agency staff in the Sri Lankan capital Colombo "did not perceive the prevention of killing civilians as their responsibility".
The panel said it had identified "systemic failures", and described the UN crisis-management structure as "incoherent".
The 30-year-long conflict between the Sri Lankan government and the separatist Liberation Tigers of Tamil Eelam (LTTE), left more than 100,000 people dead.
During the brutal closing stages of the war, tens of thousands of civilians got caught in the crossfire, as the Army closed in and the LTTE used civilians as human shields.
A UN investigation soon after the fighting ended in May 2009 said some 40,000 people may have been killed in the final five months of battle alone.
The panel questions decisions such as the withdrawal of UN staff from the war zone in September 2008 after the Sri Lankan government warned it could no longer guarantee their safety.
Benjamin Dix, who was part of the UN team that left, told the BBC that he disagreed with the pullout.
"I believe we should have gone further north, not evacuate south, and basically abandon the civilian population with no protection or witness," Mr Dix said.
The BBC quoted one survivor of the fighting as saying: "We begged and pleaded with them (UN Staff) not to leave the area. They did not listen to us. If they had stayed, many more people would be alive today."
The report will be presented this week to UN Secretary General Ban Ki-Moon who intends to publish it and act on its recommendations, sources have told the BBC.
The United Nations is yet to officially respond.BLOG COMMENTS POWERED BY DISQUS