Fresh evidence is revealed today about how MI6 and the CIA were told through secret channels by Saddam Hussein's foreign minister and his head of intelligence that Iraq had no active weapons of mass destruction.

Tony Blair told parliament before the war that intelligence showed Iraq's nuclear, chemical, and biological weapons program was "active", "growing" and "up and running".

A special BBC Panorama program tonight will reveal how British and U.S. intelligence agencies were informed by top sources months before the invasion that Iraq had no active WMD program, and that the information was not passed to subsequent inquiries.

It describes how Naji Sabri, Saddam's foreign minister, told the CIA's station chief in Paris at the time, Bill Murray, through an intermediary that Iraq had "virtually nothing" in terms of WMD.

Sabri said in a statement that the Panorama story was "totally fabricated."

However, Panorama confirms that three months before the war an MI6 officer met Iraq's head of intelligence, Tahir Habbush al-Tikriti, who also said that Saddam had no active WMD. The meeting in the Jordanian capital, Amman, took place days before the British government published its now widely discredited Iraqi weapons dossier in September 2002.

Lord Butler, the former cabinet secretary who led an inquiry into the use of intelligence in the run-up to the invasion of Iraq, tells the program that he was not told about Sabri's comments, and that he should have been.

Butler says of the use of intelligence: "There were ways in which people were misled or misled themselves at all stages."

When it was suggested to him that the body that probably felt most misled of all was the British public, Butler replied: "Yes, I think they're, they're, they got every reason think that."

The program shows how the then chief of MI6, Sir Richard Dearlove, responded to information from Iraqi sources later acknowledged to be unreliable.

One unidentified MI6 officer has told the Chilcot inquiry that at one stage information was "being torn off the teleprinter and rushed across to Number 10."

Another said it was "wishful thinking… [that] promised the crock of gold at the end of the rainbow".

The program says that MI6 stood by claims that Iraq was buying uranium from Niger, though these were dismissed by other intelligence agencies, including the French.

It also shows how claims by Iraqis were treated seriously by elements in MI6 and the CIA even after they were exposed as fabricated including claims, notably about alleged mobile biological warfare containers, made by Rafid Ahmed Alwan al-Janabi, a German source codenamed Curveball. He admitted to the Guardian in 2011 that all the information he gave to the West was fabricated.

Panorama says it asked for an interview with Blair but he said he was "too busy."

The Spies Who Fooled the World, BBC Panorama Special, BBC1, Monday, 18 March, 10.35pm.