THE thorny issue of Iraq's weapons of mass destruction continues to dog Tony Blair.

Acknowledging that they may never be found, the Prime Minister now clings to the hope that evidence may be uncovered to show WMD were hidden, removed or destroyed before hostilities began.

It appears to be a forlorn hope. Increasingly, it looks like the principal justification for going to war against Saddam Hussein will never be substantiated.

Mr Blair may be able to deflect some criticism by saying his judgement was based on intelligence material, but ultimately he must take responsibility.

Understandably, he is now switching emphasis on justification for war to regime change. Here he is on safer ground. No one would argue that it was desirable for Saddam to stay in power.

But in the absence of WMD, it is crucial for Mr Blair's credibility that regime change goes ahead smoothly.

Doubts over the wisdom of military engagement in Iraq will subside if terrorist activity reduces, if the new Iraq administration becomes firmly established and if some sense of normality is restored for the Iraqi people.

However, if chronic instability remains and British forces stay there past the medium term, the wisdom of going to war will come under fierce scrutiny.

If that happens, attention will revert to Mr Blair's insistence that Saddam Hussein's WMD were an immediate threat to stability in the Middle East and further afield.

In such circumstances the 'dodgy dossier' will continue leave the Prime Minister on dodgy ground.