Reveal Ashcroft's status, officials told

Cabinet officials have been told they must end the secrecy surrounding a promise made a decade ago when Michael Ashcroft, the billionaire vice-chairman of the Conservative Party, was awarded a life peerage.

As a condition for taking his place in the House of Lords, Mr Ashcroft promised to end his tax-exile status and become a UK resident, but in the intervening 10 years, he has refused to say whether he has kept that undertaking.

All attempts by Labour politicians and journalists to get government agencies to say whether Lord Ashcroft is a British taxpayer have met with a wall of silence, on the grounds that an individual's residence and tax affairs are private.

But the Information Commissioner, Christopher Graham, has now ordered the Cabinet Office to release the information it holds about the private exchanges that took place before Lord Ashcroft was made a peer.

The billionaire, who founded his business empire in the former British colony of Belize, is now a vital figure in the Conservative Party's election machine. He has an office beside David Cameron's at Conservative Campaign Headquarters and for months has been in charge of Tory strategy in marginal seats.

He has donated £5m to the Tories, and was by far their biggest donor during the lean years after the election defeat in 1997, earning the gratitude of the then party leader, William Hague, who nominated him for a life peerage in 1999.

Unusually, the nomination was blocked by the Lords Honours Scrutiny Committee, which then had a veto over the award of peerages. No reasons were given officially, but Lord Ashcroft has claimed in his autobiography that one reason was that he was a tax exile.

When he was awarded a peerage a year later, on Mr Hague's insistence, Downing Street added an unprecedented caveat that "in order to meet the requirements for a working peer, Mr Michael Ashcroft has given his clear and unequivocal assurance that he will take up permanent residence in the United Kingdom again before the end of the calendar year. He would be introduced into the House of Lords only after taking up that residence".

The Labour MP Gordon Prentice has spent more than two years battling to find out to whom Lord Ashcroft gave that promise, and whether it was made verbally or in writing.

He submitted a freedom of information request to the Cabinet Office in November 2007 but was told in January 2008 that it had been turned down because it involved "information provided in confidence". Mr Prentice immediately lodged an appeal, which was turned down in March 2008.

He then put in a complaint to the Information Commissioner, which has taken nearly two years to process. In his 36-page judgement, the Commissioner also criticised the Cabinet Office over the delays.

Mr Graham rejected the view that the promise Lord Ashcroft made 10 years ago is a private matter, because it involved the award of a life peerage and because its existence had been made public by Downing Street at the time. He also pointed out that it has caused years of speculation over whether Lord Ashcroft has kept the promise, which has not been cleared up by the ambiguous answers given by senior Conservatives when questioned about Lord Ashcroft's tax status.

David Cameron said last month: "Lord Ashcroft's tax status is a matter between him and the Inland Revenue. What I can say and what he has said is that the undertakings he gave at the time of being made a peer are undertakings that he is meeting."

A spokesman for Lord Ashcroft was not available yesterday.