Gordon Prentice: Ashcroft has fallen into line, and a wrong has been righted

Michael Ashcroft has now admitted he is a non-dom. Yes, he pays UK tax, but only on his UK income, not on his vast worldwide wealth. Millions that should have gone to the Inland Revenue have been channelled into the key marginals such as my own in Pendle that will decide the next election.

It is not just that Ashcroft provided the money. He has formulated and directed the strategy too – setting out a game plan on how to win the swing constituencies by a sustained, long-term campaign running over years, not weeks or months.

An outpouring of propaganda has engulfed my Pendle constituency for years: full-colour tabloid newspapers – "Pendle Matters" – delivered by the Royal Mail to all 37,000 households; surveys; leaflets. Funded by a tax exile. Ashcroft was determined to buy the next election as he had already bought the Tory party.

In a bravura performance yesterday, David Cameron told the world that he was delighted that Ashcroft has clarified his tax status. Excuse me? But why didn't the Conservative High Command quiz Ashcroft before now? Because it suited their purpose not to know and not to ask.

Cameron, William Hague and others are complicit in this decade of deception. In 1999, Hague, then Leader of the Conservative Party, nominated Ashcroft for a peerage, but he was turned down by the propriety watchdog, the Political Honours Scrutiny Committee. Yet Hague needed Ashcroft's millions so the following year he tried again.

This time, in 2000, Ashcroft promised to become a "long-term UK resident" with all that that entails. Its ordinary meaning would imply UK domicile, an attachment to the nation in whose Parliament he sought to sit. Instead, he freely admits that Belize is where his heart is.

Despite their talk of openness, the Conservatives would have kept their lips sealed had it not been for my Freedom of Information request which, after three years, has finally prised the answers out of them. They did everything to close the story down. Ashcroft's lawyers were in contact with the Information Commissioner throughout his investigation. But I was quietly confident, though hugely frustrated at the length of time everything was taking.

I wanted two very straightforward pieces of information which, in themselves, did not compromise the secrecy of the process which put a Commoner, like Ashcroft, into ermine. I simply wanted to know the form of Ashcroft's undertaking and the person to whom it was given. Once revealed, I was convinced that this would trigger further questions that would have to be answered.

To my mild surprise, the Information Commissioner did the job for me when he branded the Conservatives' earlier explanations "evasive and obfuscatory". Predictably, the Conservative leadership is now laying a smokescreen, pointing to Lord Paul, a non-dom whose businesses it tells us have given money to Labour. But Lord Paul isn't a vice-chair of the Labour party. He is not masterminding Labour's key seat strategy or bankrolling the party. And, to the best of my knowledge, he did not give any undertakings when he was elevated to the peerage – by the Conservatives.

My own view is clear. It is a disgrace that tax exiles sit in Parliament. I was outraged that another vice-chair of the Conservatives, Lord Laidlaw, had given millions to the party despite being a tax exile in Monaco. With Laidlaw and Ashcroft in mind I tried to change the law two years ago. But my private member's Disqualification from Parliament (Tax Status) Bill ran into the usual procedural sands. But now, at long last, the law is being changed. And not before time.

The Revenue, and the Courts, are now casting the net ever more widely, looking at "patterns of lifestyle" in determining residency for tax. Are the links with the UK strong enough for someone to be paying full tax?

In the longer term, we need to sweep away the opaque and overlapping concepts of domicile, UK residency and UK residency for tax purposes. The answer is to link UK citizenship with taxation of worldwide income and assets. Otherwise Ashcroft and people like him will continue to take us all for fools.

The Conservatives can start to make amends by paying back the Ashcroft millions – not to the man himself, who doesn't need it, but to the Revenue and Customs, who do.

We have all had our bellyful of tax dodgers. I know I have.

Gordon Prentice is the Labour MP for Pendle