Colin Powell highlighted the claim that Saddam Hussein had used 1,600 prisoners on death row as guinea pigs for his biological and chemical weapons program as an indication of how the Iraqi dictator's "inhumanity" had no limits.
But last night, it emerged that this part of Mr Powell's testimony to the security council was old news. The controversial claim had resulted in a serious dispute between Iraq and UN weapons inspectors in 1998.
Mr Powell told the UN how sources had told US agencies that the regime experimented on humans to perfect its biological and chemical weapons. He said an informant told how 1,600 death row prisoners were transferred in 1995 to a special unit for such experiments.
Mr Powell told the assembly: "An eyewitness saw prisoners tied down to beds, experiments conducted on them, blood oozing around the victims' mouths, and autopsies performed to confirm the effects on the prisoners. Saddam Hussein's humanity - inhumanity has no limits."
In early 1998, one of three UN weapons inspectors' teams was searching for evidence that Iraqi prisoners were deliberately exposed to chemical and biological agents.
Iraq gave documents to the UN admitting it had experimented on animals in 1995 but it denied using humans. Iraq then accused some of the British and American members of the team of espionage and refused the team access to installations where files on suspected experiments were stored. The inspectors were prevented from visiting Abu Gharib jail, near Baghdad, to investigate evidence that prisoners had been sent away for experimentation.
The Unscom team, led by American expert Scott Ritter, left Iraq because it had been blocked in its attempts to complete its mission. The obstruction led to the aircraft carrier Invincible being ordered to the Gulf in 1998 in an unsuccessful attempt to put pressure on Iraq, and the inspectors did not return.
Five years ago, a scientist who had worked at the Atomic Energy Organization in Baghdad reported that weaponized chemicals and germs had been tested on Iraqi prisoners, mostly Kurds and Shias in Radwania jail in Baghdad.
It was also reported that scientists at Salman Pak, a military complex 50 miles southwest of Baghdad, conducted experiments on Iranian prisoners of war. The claims were always denied by Iraq.
Last night, a spokeswoman for Amnesty International said it had no recent reports of such experiments: "We are aware that that did happen, but it happened in the 1980s. Prisoners were being experimented on, but as far as we know it's not something that is actually happening currently. We do know of political prisoners who are being subjected to systematic torture but as far as we know there are no transfers of prisoners for experiments."
A spokeswoman for the Foreign Office said it had no records of such experiments on its file of Iraqi human rights abuses.
© Guardian Newspapers Limited 2003