Forgive me if I tread carefully here, for while the Lib Dem deputy leader is protected by the cloak of Parliamentary privilege your humble scribe has no wish to tangle with a billionaire. So I’ll let The Times tell the story of today’s (Deputy) Prime Minister’s Questions:

A senior Liberal Democrat today referred to Lord Ashcroft, the Tory deputy chairman, as a “non-dom” in the Commons. It is the first time the Conservative peer, whose tax status is unknown, has been described in a such a way on the floor of the House.

Vince Cable, Lib Dem Treasury spokesman, used the protection of parliamentary privilege to label Lord Ashcroft. It is understood that his party has no evidence to back up Mr Cable’s claim. But party sources said that the Tory party’s failure to state whether Lord Ashcroft paid tax in this country or not has prompted Mr Cable speak out.

Lord Ashcroft is one of the Conservatives largest donors. His business empire is based in Belize, where he has citizenship, although he also has a British passport. He has declined to elaborate on personal tax matters.

The last recorded account of Lord Ashcroft’s main residence by parliamentary authorities comes from the House of Lords’ annual report on peers’ expenses in 2003-04. It was Belize.

The Tory Party is under investigation by the Electoral Commission for accepting donations from his company, Bearwood Corporate Services.

You can watch Vince in action at today’s DPMQS here:

Here’s how the full exchange was recorded in Hansard:

Dr. Vincent Cable (Twickenham) (LD): May I add our condolences in respect of the two servicemen who died serving this country in Afghanistan?

One of the Government’s achievements is that the share of tax revenue in the economy has now fallen to the lowest level since the days of Harold Macmillan. Yet, this week, Her Majesty’s Revenue and Customs estimated that about £40 billion is not being collected and is being evaded. Where is that money? [Interruption.]

Ms Harman rose—

Mr. Speaker: Order. I ask the Leader of the House to wait. Government Back Benchers are in an especially boisterous mood today, but I want to make progress down the Order Paper and get as many people in as possible.

Ms Harman: As the hon. Gentleman knows well, tax revenue has fallen because if fewer houses are being bought and sold, stamp duty falls, and if unemployment increases, there are fewer people paying taxes. Corporation tax has also fallen. Tax revenue has fallen because this country has been hit by a global economic recession.

We have been determined to take measures to stop tax avoidance, and we think it important that an example be set not only in this House, but in the House of Lords. According to an old saying, there should be no taxation without representation. What about no representation without taxation? We will introduce legislation to ensure that people are domiciled, resident and ordinarily resident in order to sit in this House or in the House of Lords.

Dr. Cable: I take that point, but perhaps make it in a less partisan way—[Interruption]—and perhaps commend the leader of the Conservative party for the helpful suggestion of new legislation, based on Liberal Democrat proposals, so that Members of the Houses of Commons and Lords who are non-doms should not sit in Parliament. May I welcome the fact that there is such enthusiasm, from turkeys voting for Christmas, and suggest that the Leader of the House give immediate effect to their wishes, by bringing in an amendment to the Constitutional Reform Bill, so that non-doms such as Lord Ashcroft can leave Parliament immediately?

Ms Harman: We certainly need transparency on the issue, and as I said, we will bring forward legislation. The hon. Gentleman is busy commending the Conservative party; at the risk of being accused of being partisan, I would like to complain about the Conservative party. The deputy chairman of the Conservative party made a promise to the honours committee—this pertains to the need for legislation—that he would make his tax affairs on shore. The Foreign Secretary—[Interruption]—the shadow Foreign Secretary—can tell us what the shadow Chief Secretary to the Treasury says he knows. Has Lord Ashcroft—

Mr. Speaker: Order. I am grateful to the right hon. and learned Lady, but we need not pursue that point any further.