DENVER -- A Colorado ranch owned by billionaire Philip Anschutz is at the center of a growing political scandal in the United Kingdom.

Eagle's Next Ranch near Kersey was visited by John Prescott, the UK's deputy prime minister last year and the visit raised questions about his connection with Anschutz and his failure to report the visit.

On Thursday, Parliamentary Standards Commissioner Sir Philip Mawer launched a full inquiry into the allegations against Prescott.

The announcement came after Prescott denied any impropriety in his relationship with Anschutz, who is hoping to build a super casino in London's Millennium Dome, according to British press reports.

Prescott and some of his civil servants spent a night at the Colorado ranch in July 2005. According to BBC News, Prescott said he wasn't on official business, so he did not need to declare the visit as required by English law.

English lawmakers are still deciding on Anschutz' request to build a super casino. He bought the Millennium Dome, on the banks of the River Thames in London, in 2003 and that is the mostly likely spot for the casino, according to British press reports.

In addition to the Colorado ranch visit, Prescott -- the equivalent of the U.S. vice president in the U.K. -- admitted meeting with Anschutz seven times since 2002, according to press reports.

"John Prescott used his influence to promote a billionaire American's bid to run a super casino in the Millennium Dome," The Daily Mail newspaper of London reported on Wednesday.

A reporter from the Daily Mail arrived in Greeley Wednesday to research the ranch. The BBC contacted 7News the same day to ask for any videotape of the ranch.

The report on the investigation by the Parliamentary Standards Commission is expected to be completed by July 25.

Prescott has been Tony Blair's deputy prime minister since 1997.