Updated

Democratic Rep. William Jefferson should be investigated by the House ethics committee, Democratic leader Nancy Pelosi said following the second guilty plea from a federal probe of alleged bribery involving the Louisiana congressman.

Pelosi, D-Calif., said at a news conference that she had not spoken directly to Jefferson about the investigation. "But he knows what is going on, and the ethics committee should investigate what is going on."

At the same time, Pelosi sought Thursday to differentiate the Jefferson case from what Democrats have labeled the "culture of corruption" linking the Republican majority and special interests represented by disgraced former lobbyist Jack Abramoff. "The Republicans are all tied together," she said. "Mr. Jefferson is his own behavior, he is responsible for it."

On Wednesday the chief executive of a Louisville-based telecommunications firm pleaded guilty to paying more than $400,000 in bribes to a congressman in a case stemming from the Jefferson investigation.

Prosecutors said Vernon Jackson, 53, funneled money over a four-year period into a company controlled by the congressman's wife in exchange for help promoting his company's technology in Africa.

In January a former legislative director for Jefferson pleaded guilty to aiding and abetting bribery of a public official and conspiracy.

Jefferson has maintained his innocence. In a statement Wednesday he said he "was surprised and disappointed to learn of Vernon Jackson's guilty plea and of his characterization of our relationship. As I have previously stated, I have never over all the years of my public service accepted payment from anyone for the performance of any act or duty for which I have been elected."