A claim that US bribery law was broken when John Prescott stayed at the ranch of Philip Anschutz is "ridiculous", the tycoon's spokesman has said.
Mr Anschutz wants to see a super-casino at the Dome
Mr Anschutz, who wants the UK's first super-casino to be in the London Dome, has been reported to the US Department of Justice over the deputy PM's visit.
But the allegations are politically motivated and "fail the common sense test", said Mr Anschutz's spokesman.
UK-based businessman George Bathurst is understood to have made the complaint.
A spokeswoman for the Justice Department said the allegation had been made via an e-mail account for complaints.
"Those complaints and allegations are reviewed and referred to the relevant people and we decide whether or not to take action," she added.
The spokeswoman added that she could not comment on "internal deliberations".
Mr Bathurst was one of the people who complained to the Metropolitan Police in London that Mr Prescott had broken the Prevention of Corruption Acts.
Last month detectives decided not to proceed with a criminal investigation into those allegations.
This decision had "completely exonerated" Mr Anschutz, the tycoon's spokesman said, adding that all claims of wrongdoing against him were "utterly false".
He said the company does not own or operate casinos - if the go ahead was given for a super-casino in the Dome another company is expected to seek a lease to operate one there.
He also referred to the cowboy outfit which was given to Mr Prescott during his trip.
"While investing as much as £650m in London and regeneration of the Greenwich peninsula, would a company even think about influencing a government official with some Western clothes? Of course not."
Mr Prescott was criticised by the Commons standards committee in July for failing to immediately declare his trip.
Mr Prescott has always denied any accusations of wrongdoing
But he strongly denied any conflict of interest, saying he was not involved in decisions about the Millennium Dome site.
For the Conservatives, shadow culture, media and sport secretary Hugo Swire said it was "highly embarrassing" for Mr Prescott "to be part of a corruption investigation in the United States".
"We will be watching closely to see if this throws any new light on this government's close relationship with overseas casino operators," he added.
Breaking the laws which ban American businessmen from trying to bribe foreign officials carries a punishment of up to five years in jail.