Donald Rumsfeld had the chance when he was US defence secretary in December 2001 to make sure Osama bin Laden was killed or captured, but let him slip through his hands, a Senate report has found.

The report by the Senate foreign relations committee is damning of the way George Bush's administration conducted the aftermath of its bombing campaign in Afghanistan, saying it amounted to a "lost opportunity". It states that as a result of allowing the al-Qaida leader to flee from his Tora Bora stronghold into Pakistan, Americans were left more vulnerable to terrorism, and the foundations were laid for today's protracted Afghan insurgency. It also lays blame for the July 2005 London bombings on a failure to kill the al-Qaida leaders at Tora Bora.

Republican critics are likely to dismiss the report as a partisan work designed to deflect the current military troubles in Afghanistan away from President Barack Obama and on to his predecessor. The committee is Democratic-controlled.

But the report contains a mass of evidence that points towards the near certainty that Bin Laden was in the Tora Bora district of the White Mountains in eastern Afghanistan, along with up to 1,500 of his most loyal al-Qaida fighters and bodyguards, in late November 2001, shortly before the fall of Kabul.

Further evidence came from al-Qaida suspects detained at Guantánamo and, most authoritatively, from the official history of the US special operations command, which confirms bin Laden's presence at Tora Bora.

"Osama bin Laden's demise would not have erased the worldwide threat from extremists," it concludes. "But the failure to kill or capture him has allowed Bin Laden to exert a malign influence over events in the region."