Analysis By Nick Assinder BBC News Online political correspondent

It is pretty plain that he would rather it was not near the top of the political agenda in the first place - primarily for fears it can all too easily fan the flames of racism and xenophobia.

And there is no certainty that, when the debate is engaged, he will be able to persuade voters to accept his reassurances that abuses of the system are limited and that immigration as a whole is a good thing for Britain.

He even confessed during his press conference that he had always believed there would come a moment when, politically, there had to be a debate about this most sensitive of issues.

Presumably because he is well aware just how powerfully the issue can play with alarmed voters - particularly when deployed in what he would view as an irresponsible manner.

It has featured in previous local and general election campaigns, with hard right groups - notably the BNP - exploiting public fears for electoral advantage.

And there have always been what Mr Blair sees as inflammatory stories about immigration carried by some sections of the media.

He is confident those figures will prove once and for all that managed migration into Britain is indeed of net benefit to the country

Previously there has been an apparent reluctance by many politicians, particularly Labour, to engage too robustly in this argument.

But the prime minister has now apparently decided - particularly after the crisis which led to the resignation of minister Beverley Hughes - that it can no longer be avoided.

So, as he demonstrated in his press conference, he and his ministers will now launch a campaign of persuasion by setting out the facts.

He unveiled a series of initiatives aimed at tackling the accepted abuses of the system, highlighted by the revelations from Eastern European countries.

But many of them were not new and Tory spokesman David Davis had already predicted they would be re-announced and, as a consequence, dismissed them.

Powerful weapon

Probably the most important announcement from the prime minister was that he had ordered the National Audit Office to review all the statistics so he can present the real picture of immigration in Britain.

That, he hopes, will provide him with a powerful weapon to take on his opponents in the Tory party and the more extreme elements seeking to whip up this row.

This is an issue that stirs emotions, irrespective of what the statistics may suggest

He is confident those figures will prove once and for all that managed migration into Britain is indeed of net benefit to the country and that abuses are relatively small.

That is no small or easy task. Statistics are always open to interpretation and, more worryingly, this is an issue that stirs emotions, irrespective of what the statistics may suggest.

So the prime minister has a major battle on his hands.

And one that looks like it may well run through the summer's local and European parliament elections into the general election campaign beyond.

Meanwhile, however, the claims about who knew what and when about the abuses in Eastern Europe will continue to chew at the government.

The underlying suggestion is that ministers connived in the waving through of immigrants from these countries as part of a campaign to ensure any future "flood" of migrants is reduced to an un-controversial trickle when they join the EU.

That suggestion has not gone away and Mr Blunkett still finds himself at the centre of suggestions that either he must have must have known what was going on - and therefore misled MPs when he denied it in the Commons - or that he had lost control of his department.

It was that row which did for Ms Hughes and the Tories still have their sights on Mr Blunkett.

For the moment, however - and barring any fresh revelations - the heat seems to have gone from that issue.