Gossip from an Iraqi taxi driver was a key source for Tony Blair's 'dodgy dossier'.
A report by a respected MP claims that the unlikely secret agent was one of MI6's top sources when it was building a case to justify the invasion.
He provided the information that Saddam Hussein could fire chemical weapons at British targets within 45 minutes.
The revelation comes as the death toll of British troops in Afghanistan reaches 100 this year alone following the shooting of a member of 1st Battalion The Royal Anglian Regiment in a gun battle with the Taliban.
Senior intelligence officials have told the MP that the cabbie falsely claimed Saddam Hussein had acquired long-range missiles after listening to Iraqi commanders chatting in his taxi two years before the invasion.
The driver, who worked near Iraq's border with Jordan, was allegedly the 'sub-source' of a senior Iraqi military officer who told MI6 that Saddam had battlefield chemical weapons ready to deploy at 45 minutes' notice.