The UN's former chief weapons inspector in Iraq has suggested Mr Tony Blair was exaggerating the threat posed by international terrorism.
Dr Hans Blix urged caution over the doctrine of pre-emptive strikes against states suspected on the basis of intelligence of backing terrorism or developing illicit weapons.
The intelligence used to justify war in Iraq had turned out to be wrong, but the US and UK had acted like "witch-hunters", preferring to believe their fears rather than the evidence presented to them, he said.
Dr Blix last week heightened pressure on Mr Blair over Iraq by revealing he believed the war was illegal. His comments now come days after the Prime Minister's passionate speech in defence of the conflict, in which he warned the world faced "mortal danger" from terrorists prepared to wage "war without limits".
Mr Blair predicted world leaders would have to rely ever more heavily on intelligence to warn them of dangers to global security and urged the UN to consider changing international law to permit intervention in states which posed a threat.
Asked about Mr Blair's comments, Dr Blix told BBC1's Breakfast with Frost: "I think we still over-estimate the danger of terror.
"There are other things that are of equal, if not greater, magnitude, like the environmental global risks.
"When Blair says intelligence is becoming ever more important, then I think we have to be careful."
Dr Blix cast doubt on Mr Blair's claim that changes to international law were needed to permit intervention to prevent atrocities in states like Rwanda.
This month's swift deployment of international troops to Haiti showed the UN had the powers it needed to act in such cases, he said, adding: "Intervention in Rwanda was probably hindered more by the lack of will to spend the resources. That is more the inhibition than the UN charter."