Swept into office partly on promises to end a “culture of corruption,” many potentially vulnerable Democratic newcomers are pressing House leaders to confront allegations of unethical conduct involving fellow Democrats.

Discontent over ethics has been underscored in votes on Republican-sponsored privileged resolutions calling on the House ethics committee to probe the ties between the defunct lobbying firm PMA and powerful Democrats including John P. Murtha , Defense Appropriations Subcommittee chairman.

Democrats have rejected the resolution eight times, most recently on May 12. But 29 Democrats — including 22 first elected in 2006 and 2008 — voted for the measure sponsored by Rep. Jeff Flake , R-Ariz.

Almost a third of the 34 Democratic freshman, or 11 members, bucked their leadership, which has pressed rank-and-file members to oppose the resolution, saying that if Republicans have a gripe, they should file a complaint with the Committee on Standards of Official Conduct.

Another unsuccessful GOP measure offered just before the Memorial Day recess would have barred funding for the lightly used John Murtha Johnstown-Cambria Airport, a facility in Murtha’s district. Murtha has used his perch on the Appropriations Committee to steer considerable federal funding to the facility. That measure, too, won support of 11 Democrats, all but one first elected in 2006 and 2008.

Rep. Tom Perriello , a 34-year old freshman Democrat from southwest Virginia who backed both measures, said that while he understood Republicans were involved in “some partisan game playing,” he wanted to send a message that he backed reform.

“We want clean government. A lot of us ran on that. We think the rules are still broken,” Perriello said.

In the 2008 elections, Perriello narrowly edged out GOP incumbent Virgil H. Goode, Jr. after campaigning that he wanted to replace “the culture of corruption” with “the culture of service.”

Stuart Rothenberg, editor of the non-partisan Rothenberg Political Report, said that the rebellion among newer members indicates a nervousness about their future electoral prospects as well as a generational divide over how lawmakers should do business.

“There is a line of fracture within the party. These newcomers — they are more ethics-sensitive than the guys who have been in there two or three decades,” he said.

The 76-year-old Murtha was first elected in 1974 and over the years has amassed considerable power as a defense appropriator responsible for doling out hundreds of billions in federal funds. Over the years he has remained popular in his southwest Pennsylvania district, by bringing substantial federal funds in form of earmarks and other grants to an area hit by industrial decline.

Most of the newcomers who voted for the Flake resolution were elected in districts previously represented by Republicans and likely face competitive races in 2010. The resolution has attracted limited but growing Democratic support since it was first introduced earlier this year. The two latest defectors were elected this spring in special elections: Scott Murphy of upstate New York and Mike Quigley of Illinois.

When Republicans controlled the House from 1995 to 2007, Democrats made a big issue of the majority’s ethical woes. Democrats hammered Republicans for their ties to K Street, particularly lobbyist Jack Abramoff, who was sent to prison after pleading guilty in 2006 to various corruption charges.