Rep. Bob Ney, R-Ohio, is nicknamed the "mayor of Capitol Hill." He chairs the powerful House Administration Committee, which controls offices and perks.
In February 2003, Ney took a three-day trip to London. Following House rules, he reported the trip cost $2,707 and was paid for by FN Aviation. Nigel Winfield is the group's director.
NBC News has learned that Winfield, who met with Ney in London, is a three-time convicted felon who spent more than six years in prison. He cheated on his taxes and was involved in a deal to swindle Elvis Presley.
In a telephone interview, Winfield told NBC News he wanted Ney's help selling planes in the Middle East.
"My only interest was trying to meet a congressman and see what we could do," says Winfield.
In London, Winfield says Ney attended meetings, one over dinner at a casino with Winfield and Fouad al-Zayat, a Syrian-born businessman who heads FN Aviation. Zayat is one of London's biggest gamblers, betting hundreds of thousands of dollars on roulette in a sitting.
Experts say Ney's trip may violate House rules.
"The ethical problem will be: Did the trip consist of something connected to his official duties, or was it simply a foreign romp to go gambling?" says former House Ethics Committee counsel Stan Brand.
"I, for one, think that the House Ethics Committee needs to examine all of Mr. Ney's travel for the past several years, and examine his conduct and make sure it was all above-board," says Melanie Sloan, executive director of Citizens for Responsibility and Ethics in Washington.
Thursday, NBC asked Ney about the trip.
"I have no comment for you," he said to our camera crew on Capitol Hill.
Did he know Winfield was a felon?
"No, I had no knowledge of that. No," he replied.
In retrospect, was this trip a good idea?
"You have to talk to my office. Thank you."
That same year, Ney reported that he won $34,000 at the very same London casino on an initial bet of $100. In 2002, Ney had reported at least $30,000 in credit card debt. In 2003, he reported he'd paid it off. His lawyer says Ney won that money gambling on a separate trip to London, not the one involving FN Aviation.
NBC News tried to interview Zayat at his offices in Cyprus and London, but he was not available for comment.
Ney's lawyer insists the trip was entirely proper and consistent with House rules. However, he says the congressman can't discuss his activities because of "national security implications."