By Barnaby Mason
BBC diplomatic correspondent
Former archbishop of Cape Town and Nobel peace prize winner Desmond Tutu says the "immoral" war in Iraq has left the world a much more unsafe place.
The archbishop made one of his most outspoken attacks against the war
Desmond Tutu urged US President George Bush and British Prime Minister Tony Blair to admit they had made a mistake.
The archbishop also demanded to know whether it had been right to attack Iraq in defiance of international law.
Archbishop Tutu's severest criticism of the war yet came in a lecture to the Prison Reform Trust in London.
Desmond Tutu has made several critical comments about the Iraq war and its aftermath since beginning a short stint as a visiting professor at London University.
In this lecture he was at his most outspoken.
He said belligerent and militarist policies had produced a novel and dangerous principle - that of pre-emptive attack on the basis of intelligence reports.
In the case of Iraq, Archbishop Tutu said, the intelligence had been flawed - yet it was the basis for the United States going to war dragging Britain behind it.
He also criticised the alternative justification of ousting a tyrannical regime.
He demanded to know by what authority President Bush and the British Prime Minister, Tony Blair, had acted; was it might is right, and to hell with international law?
Desmond Tutu brought this onslaught into a lecture arguing that retribution was a poor basis for a penal system and arguing for the kind of restorative justice seen in South Africa's Truth and Reconciliation Commission, which he chaired.
Archbishop Tutu referred to the idea that harsh prison sentences made people safer.
In the invasion of Iraq, he said, they could see the same illusion on a global scale - that force and brutality could produce security.