The US and the UK are accused of relying on questionable information that suggested Saddam Hussein was manufacturing weapons of mass destruction (WMD), despite warnings over its authenticity.
According to a BBC Panorama investigation, at the same time, other foreign intelligence that suggested no such programme existed was dismissed.
An Iraqi spy, code named 'Curveball', who claims to have witnessed the manufacture of WMD, told the programme the invasion had been based on his 'lie'.
According to The Telegraph, Lord Butler, who, a year after the invasion, carried out a British review of the intelligence used, admitted that he was unaware that two senior members of Saddam's regime had secretly told the CIA and MI6 that WMD did not exist.
One source told the programme that the conflict was borne out of 'choice' rather than 'necessity'.
'BBC's Panorama: The Spies Who Fooled The World' reports how claims from a few sources that Iraq was manufacturing WMD spiralled into apparently sound intelligence that was used to justify the war.
According to the report, in his first TV interview on the subject, August Hanning, the former head of German intelligence, said that Curveball, whose real name is Rafed Al Janabi, told the German secret services that he had witnessed the manufacture of chemical and biological weapons.
The information was passed by the Germans to American and British intelligence, along with concerns about its reliability, he said.
Joschka Fischer, the former German foreign minister, said US colleagues were warned about the information. However, he told Panorama that 'they were not in a state, or a mindset to be warned'.
London: Key intelligence that was used to justify Iraq's invasion 10 years ago was based on 'fabrication and wishful thinking', a documentary is set to claim.
First Published: Monday, March 18, 2013, 18:56