By Nick Assinder BBC News Online political correspondent

Today he stood in the Commons during his weekly question time clash with the prime minister - and didn't.

It must count as one of the greatest disappointments of the year, so far.

After all, it is not every day the leader of the opposition calls for the head of a prime minister.

It is seen as the nuclear option, only ever to be deployed under two circumstances.

Any certainty?

One, when the alleged offence is so severe no other course of action is reasonable or to be expected.

And two, when you are pretty certain the prime minister is about to do it anyway.

Rightly or wrongly, Mr Howard may well feel confident about the first question - in regard to what the prime minister did or did not know about Iraq's weapons of mass destruction before he took the UK to war.

He is presumably far less certain about the second one.

So the "resign" call never came - much to the disappointment of many on the Tory benches, a few on the Labour benches and just about everybody in the press gallery.

'Headache'

Fear not, however. Despite the prime minister's best efforts, Iraq has not gone away and, to coin a phrase, Mr Howard "will be back".

In the mean time he decided instead to repeat his previous week's question over what the government was going to do to stop an influx of benefits shoppers coming to Britain from the new EU states in the summer.

This issue is patently giving the government a headache.

It wants to allow new immigrants to fill skills shortages, it does not want an influx of so-called "benefits shoppers" and, probably most important of all, it does not want top attract newspsper headlines about being Europe's soft touch.

An announcement has been expected from Home Secretary David Blunkett about all this some time this week - but it will not now happen and looks unlikely for many days ahead.

So, not surprisingly, the prime minister dodged a bit.

Union cash

Things warmed up a bit when Mr Howard demanded to know why the government was planning to hand the unions up to �10m in cash to "modernise".

Why on earth not, suggested the prime minister. We give business similar grants, it is good to encourage better employer-employee relations.

And in any case, the government gives the opposition loads of cash through the so-called Short money. So there.

There is a definite feeling that Michael Howard's honeymoon is drawing to a close.