Commons sketch By Nick Assinder BBC News Online political correspondent

Someone might have to separate Blair and Howard

While the builders are at it, they might like to put a similar barrier between Tony Blair and Michael Howard.

The aggression count between the two men has steadily increased over the weeks until - fanned by the row over the allegedly chaotic immigration system - it has now approached something like critical mass.

Mr Howard appeared genuinely seething that the prime minister's now near-traditional response to each crisis is to set up an inquiry and then, pending its report, refuse to answer questions on the issue at hand.

This time Mr Howard had clearly been hoping to pile the pressure onto beleaguered immigration minister Beverley Hughes, her boss David Blunkett - who has effectively tied his future to hers - and even the prime minister himself.

And, despite a series of inquiry-itis answers from Mr Blair, he probably succeeded in drawing some more blood.

Rabble level

Each time he levelled a specific allegation, the prime minister came back with a "wait for the outcome of the inquiry" answer.

Howard seemed genuinely affronted

That so infuriated Mr Howard he spat back: "I am just asking for some straight answers to some straight questions.

"He has to learn he cannot avoid giving straight answers from that despatch box by setting up an in-house inquiry."

The background noise from both benches reached rabble level over this and most would have to agree the prime minister - albeit loudly supported by his own benches - was on the losing side.

That is until Mr Howard appeared to link the immigration row with asylum - that gave the prime minister his opening and he went straight for it - suggesting the Tory leader was playing dangerous games with his language.

Everyone knew what he meant by that - that Mr Howard was in danger of fanning anti-immigrant bigotries, a suggestion Mr Howard would vehemently reject.

Easter break

Then Mr Blair fell back on his other trick of calling on Mr Howard to get to his feet and deny something, knowing the opposition leader had run out of his allotted six questions.

At least the spat allowed Liberal Democrat leader Charles Kennedy to focus on the other issue buffeting the government, namely the following vote on tuition fees.

The policy would deter youngsters from going to university in the first place, represent a breach of trust with voters who had been reassured Labour would not introduce it and would, in any case, not solve the problem of university funding, he said.

But, inevitably, it was the immigration clash which dominated and, despite all the ducking and weaving, this is an issue that will not go away. Even the internal Home Office inquiry is unlikely to put an end to it.

The Tories may think they can get Ms Hughes' scalp on this, alternatively they may be happy for her to stay in place as an allegedly busted flush.

The prime minister may be relived that the Commons is just about to break for an unusually long two week Easter break - to allow that screen to be erected - and he will not have to face Mr Howard until 15 April.