Unless they defuse the issue, the Tories will face Ashcroft questions every day until the election

If PMQs today showed anything, it's just how eager the Tories' opponents are to bring up the issue of Lord Ashcroft.  Vince Cable set the ball rolling by referring to the Tory deputy chairman as a "non dom", and Harriet Harman gleefully followed up by firing questions in William Hague's direction.  She was cut off – and rightly so – by John Bercow.  But the insinuations about the Lord and his tax status had already been made.

Now, you could say that this is pretty low stuff from Labour and the Lib Dems.  After all, David Cameron pledged earlier this week to legislate so that all MPs and peers are UK taxpayers.  And a spokesman for Ashcroft responded: "This will not represent a problem for Lord Ashcroft who looks forward to many happy years in the House of Lords."  Just what more could be said or done?

But it's clear now that Labour and the Lib Dems will keep pushing the Ashcroft line of attack, from now until the election, regardless of what the Tories promise to do in government.  In that light, the fact that Cameron and Ashcroft refuse to clear up his tax status, once and for all, remains a gross strategic liability.  Not only does it give their political opponents a chance to land blows, but it could rile those Tories who think Ashcroft is being given special treatment.  What's more, it's hard to think of any upside to the current approach for either the Cameroons or Ashcroft himself, who will come under under ever more intense media scrutiny.

We do tend to make this point quite a lot on Coffee House, but, in view of the Tories' intransigence, it's a point worth repeating.  Cameron and Ashcroft really do need to come to come clean.