The Conservatives are demanding that the Parliamentary Commissioner for Standards should investigate the trip to the 32,000-acre Denver estate of Philip Anschutz last July.

Mr Prescott spent the night with a “small number” of civil servants at Mr Anschutz’s home, which has its own nine-hole golf course, hunting facilities and a health spa. The visit was on a “day off” in the middle of the nine-day, four-state trip to the US, in which he was representing the Prime Minister. A spokeswoman for Mr Prescott confirmed that the donation, which was made to a 7/7 charity, came from the public purse because the trip was official business. If Mr Anschutz had not offered his hospitality, she said, the Deputy Prime Minister and his officials would have stayed at a hotel paid for by the department.

However, his representatives have not said when the donation was made, or how much it was for.

Hugo Swire, the Shadow Culture Secretary, said: “This is completely ridiculous. Mr Prescott should be the one making the donation because he enjoyed the hospitality.

“Now it is more important than ever to know how much the donation was for. Is this really a proper use of public money?” The issue is almost certain to be raised at Culture Questions in the Commons this afternoon and Mr Swire has said that he will write to Mr Prescott asking him to clarify his relationship with Mr Anschutz.

Mr Anschutz, who has close links to President Bush, is the owner of AEG entertainment, which was handed the Dome free for 20 years in June 2004, although taxpayers are expected to receive a share of the estimated at £216 million over the course of the contract.

It is also one of the eight locations on the shortlist to become home to Britain’s first supercasino, having teamed up with the casino firm run by Sol Kerzner, a South African.

The Deputy Prime Minister’s former department oversaw planning policy for casinos, although the location of the first supercasino will be decided by an independent panel overseen by the Department of Culture, headed by Tessa Jowell.

Mr Prescott has publicly insisted that there was no conflict of interest between his ministerial role and his relationship with Mr Anschutz. “I played no role in any planning decisions relating to the sale of the Dome or in any negotiations for the sale of the Dome,” he said in a statement.

However, at the time of the US trip Mr Prescott had ultimate ministerial responsibility for the regeneration of the Dome.

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