The United Nations Secretary-General Kofi Annan has told the BBC the US-led invasion of Iraq was an illegal act that contravened the UN charter.
He said the decision to take action in Iraq should have been made by the Security Council, not unilaterally. {{more}}
And he feared elections planned for January would not go ahead in Iraq unless security considerably improved.
The UK government responded by saying the attorney-general made the “legal basis… clear at the time”.
Mr Annan said that “painful lessons” had been learnt since the war in Iraq.
“Lessons for the US, the UN and other member states. I think in the end everybody’s concluded it’s best to work together with our allies and through the UN,” he said in an interview with the BBC World Service.

‘On track’
“I hope we do not see another Iraq-type operation for a long time – without UN approval and much broader support from the international community.”
“From our point of view and the [UN] charter point of view it was illegal,” he added.
Mr Annan said the UN would give advice and assistance in the run-up to the elections, but it was up to the Iraqi interim government to decide whether such a vote should go ahead.
He warned there could not be “credible elections if the security conditions continue as they are now”.
In response, a UK foreign office spokeswoman said: “The Attorney-General made the Government’s position on the legal basis for the use of military force in Iraq clear at the time”.
Earlier on Wednesday, the head of the British army General Sir Mike Jackson said national elections in Iraq were still on track.
He told BBC Radio 4’s Today programme: “People are pretty confident that they can take place if everybody puts in the required effort and arrangements into it.”
His comments came a day after a car bomb close to an Iraqi police station in central Baghdad killed 47 people and gunmen opened fire on a police minibus in Baquba, killing 12.
At the beginning of the week, Iraq’s interim Prime Minister Iyad Allawi said elections must go ahead as planned although he conceded the violence might stop some Iraqis voting.
“If, for any reason, 300,000 people cannot vote because terrorists decide so – and this is imposing a very big if – then frankly 300,000 people is not going to alter 25 million people voting,” he told The Times and Guardian newspapers.
“There are problems, yes. But to the point that we can’t conduct an election? I don’t think so.”