House Democratic leader Nancy Pelosi on Thursday said Republicans had created "one of the most closed, corrupt congresses in history" and urged the House ethics committee to investigate GOP lawmakers linked to lobbyist Jack Abramoff.

"It's hard for the American people to understand how corrupt it is here," the California Democrat said at a news conference.

In a letter to House Speaker Dennis Hastert, R-Ill., Pelosi said Democrats expect the ethics committee to look into the "alleged violations of criminal laws and the rules of the House" by former Majority Leader Tom DeLay, R-Texas, and three other Republicans with ties to Abramoff -- Bob Ney of Ohio and Californians Richard Pombo and John Doolittle.

Abramoff has pleaded guilty to federal conspiracy, tax evasion and mail fraud charges for his influence-peddling activities, but so far no member of Congress has been indicted.

Pelosi's letter did not ask the ethics committee to investigate an unrelated case involving Democratic Rep. William Jefferson of Louisiana.

A former aide to Jefferson, in pleading guilty to aiding and abetting bribery of a public official, said Jefferson had demanded bribes for promoting business opportunities in Africa, according to court documents filed Wednesday.

Pelosi didn't comment on the Jefferson case, but stressed that "we have said all along that, Democrat or Republican, anyone who doesn't follow the rules or the law has to be held accountable. That's the difference between us."

Hastert's spokesman, Ron Bonjean, said it was "hypocritical for Leader Pelosi to throw mud" when a fundraising committee run by the Democratic leader had been fined last year for improperly accepting donations over federal limits.

He said Republicans hope Pelosi "will stop playing politics and will support our comprehensive lobbying effort that will help change the way work is done in Washington."

Hastert has asked Rules Committee Chairman David Dreier, R-Calif., to craft lobbying ethics legislation to address some of the abuses that led to the Abramoff scandal. One idea they have proposed is to bar lawmakers from accepting any privately funded trips.

Pelosi said she welcomed that proposal, "but that's only the beginning." Legislators from both parties have recommended tougher rules on accepting gifts and lengthening the period between when a lawmaker retires and can accept a job as a lobbyist.

She added that "if we are ever really going to have real change here, we must kill the K Street Project." That initiative, spearheaded by DeLay, pressured lobbying firms to hire only Republicans and direct money to Republican causes.