Former British Prime Minister Tony Blair "very much exaggerated" Iran's role in supporting al Qaida insurgents in their attacks on British and American forces in Iraq, a former ambassador to Tehran said today.
Richard Dalton said that the UK and US misread the intentions of the Iranian regime, believing it would inevitably be hostile to their mission in Iraq when in fact Tehran wanted them to succeed in installing a stable government in Baghdad.
Giving evidence to the Iraq Inquiry today, Dalton - Britain's ambassador in Tehran from 2003/06 - said Mr Blair made "a series of very bad decisions" about the legality of the 2003 invasion.
He also condemned US President George Bush's 2002 characterisation of Iran as part of an "axis of evil" as a "monstrous error".
As international pressure continues to ratchet up over Tehran's alleged efforts to acquire nuclear weapons, Dalton warned that military action against Iran would be illegal unless there was evidence it posed an "imminent and real" threat to another country.
In his appearance before the inquiry in January, Mr Blair stressed the role of both Iran and al-Qaida in destabilising Iraq and making the task of rebuilding the country following the overthrow of Saddam Hussein more difficult.
"What nobody foresaw was that Iran would actually end up supporting al-Qaida," the former British Prime Minister told inquiry chairman John Chilcot.
"What happened in the end was that they did because they both had a common interest in destabilising the country, and for Iran I think the reason they were interested in destabilising Iraq was because they worried about having a functioning majority Shia country with a democracy on their doorstep."
But Dalton today told the inquiry: "From what I saw of his evidence, I thought he very much exaggerated this factor."
Iranian help to al-Qaida was in fact limited to permitting fighters to pass across its territory from Pakistan and Afghanistan, said Dalton. His assessment was that Tehran had no interest in promoting "anarchy" in Iraq, but wanted an inclusive Iraqi-run government capable of acting as a source of stability in the region.
He added: "I did believe at the time - particularly in 2003 - there was a misreading of Iran as inevitably hostile to the success of the coalition mission to replace Saddam with an Iraqi regime that would be democratic.
"I felt at the time that the legitimate and justified criticism of Iran was sometimes used with too broad a brush. Much more of the coalition difficulties were attributed to Iran than was the case."
Iran wanted to foment enough disorder in Iraq to "make sure the coalition felt some pain and therefore didn't dig in for a long stay", but its interference was not as damaging to the US-led mission as the insurgency led by former Ba'athists.
"Their objective was never to destabilise Iraq to the point at which the whole enterprise would fail," said Dalton.
"They feared anarchy and they feared that if the handover to Iraqi politicians was to fail completely, that would be the worst possible situation for Iran, because that would allow the Americans an excuse to stay very much longer.
"They were seeking to hurt the coalition without preventing the takeover of Iraq by an Iraqi regime that would be successful."
US refusal to listen to legitimate Iranian concerns that the West was "messing in their neighbourhood" led to a damaging downward spiral in relations with Tehran, said Dalton.
He added: "I also felt at the time of Mr Blair's testimony to you that he was seeking to cast a retrospectively benign light on a series of very bad decisions taken about the legality of an attack on Iraq by saying it was not only right to do it, but we might have to do it again.
"I felt strongly then and I do now that a military adventure against Iran... would be illegal in the absence of an imminent and real threat to any country from Iran. No such nuclear threat exists at present."
Geoffrey Adams, who followed Dalton as ambassador from 2006-09, told the inquiry that senior Iranians viewed the prospect of a prosperous and stable post-Saddam Iraq not as a threat but an attractive market for their goods and services.
"The irony as they saw it is that the traditional enemies of the Iranian revolution - the UK and US - have removed the two greatest threats from the borders of Iran: the Taliban in Afghanistan and Saddam Hussein's regime in Iraq," he said.
However, he said he had been subjected to some "pretty clear threats" from Tehran over the ability of Iran's allies in Iraq to "cause discomfort" to Western interests in the country.
"I had the impression that, although some in the Iranian system recognised and understood that their true national interest was in an Iraq that was stable, nevertheless the presence of Western forces in Iraq presented Iran with an opportunity to put some pressure on the West," he said.
"One of the objectives of Iranian policy was that the coalition - and the US in particular - shouldn't be able to leave Iraq with their heads high or be able to claim legitimately that their mission had been a success."