American Radio Works’ Marketplace reported on Monday that since 1996 ten current and former federal lawmakers have participated in an annual charity event attended by powerful oil lobbyists and hosted by the charity founded by Alaska First Lady Nancy Murkowski. The report found that at least three senators neglected to report the trip to the Waterfall fishing resort, which is located deep in the Alaskan wilderness and provides some of the best fishing in the world.

The senators who failed to report the trip are Kit Bond (R-MO) and Mike Enzi (R-WY), as well as former Senator Phill Gramm (R-TX). Because of the investigation the two sitting senators have pledged to reimburse the charity. Former Senator and current Alaska Governor Frank Murkowski (R) and House Speaker Dennis Hastert have also regularly gone on the trip.

Also attending these trips are first-tier executives from oil companies, including British Petroleum, Amoco, Marathon Oil and dozens of others. Red Cavaney – President and CEO of the American Petroleum Institute, the preeminent oil lobbying group in Washington – has become a familiar face at Waterfall, too.

The event benefits the Waterfall Committee, which was founded by Nancy Murkowski. She still sits on the organization’s board. The charity pays for doctors and other health care workers to travel to remote parts of Alaska to do breast cancer screenings.

A Senate rule put into effect in 1996 prohibits senators from accepting invitations to and attending such paid charity events, because of the opportunity they provide to outside interests for lawmaker influence. A letter sent to Murkowski that year from the Senate Ethics Committee forbade him from accepting free travel or lodging to go to Waterfall, but Senators Gramm, Bond and Enzi did.

Alaska media coverage of the event following the radio story has been nearly nonexistent, even as Governor Murkowski is currently embroiled in a bitter fight to get a proposed natural gas pipeline built stretching from Alaska’s North Slope to the contiguous 48 states. Murkowski is already in deep political trouble, with sky-high disapproval ratings. In the latest Republican primary match-up he polled third of three GOP candidates, a poor showing for an incumbent less than six months before facing reelection.

Check out a picture gallery documenting the trips here.