WASHINGTON - A half-dozen federal investigations into the activities of Republican lawmakers are raising new worries for GOP leaders who hope to regain the House majority they lost last fall.

Democrats say at least six GOP House members are under some degree of Justice Department scrutiny, although Republicans doubt all the inquiries are active.

Republicans call attention to the fact that Democrats have their own ethical problems. Rep. William J. Jefferson, D-La., has been under scrutiny in a bribery investigation since at least 2005. The Justice Department also is investigating whether Rep. Alan Mollohan, D-W.Va., benefited from steering federal funds to nonprofit groups he helped start.

At a minimum, the growing list of GOP incumbents under scrutiny is a nuisance for a party struggling with an unpopular president and his handling of an unpopular war.

"It's a question of accountability," said Jennifer Crider, spokeswoman for the Democratic Congressional Campaign Committee.

Ethics cases elsewhere aren't helping Republicans. Democrats are using subpoenas to dig into the administration's firing of several federal prosecutors. They're also monitoring news reports from Alaska saying that business associates, friends and a son of veteran GOP Sen. Ted Stevens are under investigation in a long-running corruption inquiry.

The situation troubles some conservative activists. Especially under criticism is the House GOP leaders' decision to replace one embattled member of the coveted Appropriations Committee with another.

Rep. John Doolittle, R-Calif., left the committee in April after FBI agents raided his Washington-area home. His wife, Julie, ran a business from the home in which she received commissions as a paid fundraiser for her husband's campaigns.

Doolittle's committee seat went to Rep. Ken Calvert, R-Calif. The FBI retrieved copies of Calvert's annual financial disclosure statements following reports last year that Calvert steered millions of federal dollars to projects near his private real estate developments. Aside from Doolittle, Republican operatives are most concerned about Rep. Rick Renzi, R-Ariz., who gave up his House intelligence committee seat last month after FBI agents raided his wife's business.

Renzi paid hundreds of thousands of dollars in back taxes while settling charges that his businesses improperly paid for his first congressional campaign. He also faces an inquiry into whether he used his House seat to help a former business partner make land swaps.

Other Republican House members recently under scrutiny:

Jerry Lewis of California. Prosecutors in Los Angeles are examining how millions of dollars in federal contracts were steered to a company whose founders were big contributors to Lewis' campaigns while he chaired the House Appropriations Committee.

Tim Murphy of Pennsylvania. Murphy declined comment on published reports that authorities are investigating whether his legislative aides performed campaign work while on government time.

Gary Miller of California. Miller says he has no reason to believe he is under investigation, but Democrats have run Web-based attack ads citing published reports that federal agents have looked into some land deals involving the lawmaker.