But today, in sometimes halting English, Mr. Chung seemed less sinister than out of his depth in the high-stakes world of Presidential fund-raising. In five hours of testimony, he described himself as a ''first generation immigrant'' who would never ''undermine the interests of my country'' and is ''as loyal to our country as any of you.''

Mr. Chung pleaded guilty in March 1998 in a deal with the Government in which he agreed to cooperate fully. He was sentenced to a suspended jail term and 3,000 hours of community service. His testimony today under subpoena was approved by the Justice Department.

Although Mr. Chung had never testified, the broad outline of his account had been known from Congressional and Justice Department investigations. Today, he said that he accepted responsibility for his misdeeds, but that the lawmakers who had summoned him to testify were also accountable for setting up the fund-raising rules that he operated under. ''I didn't create the system,'' he said. ''You did.''

''Yet, more than two years after this controversy erupted, you, the Congress, have done nothing to change this system,'' Mr. Chung said. ''Indeed, within the last month I received an invitation to a fund-raiser where I might have yet another photo opportunity with some politician. Although most of you would probably run away from me at his point.''

Today's appearance showed how Mr. Chung's fortunes had changed since he was in favor at the White House, invited to attend the President's Saturday radio addresses, and on tours of the Oval Office and Hillary Rodham Clinton's own office. Republicans on the committee warmly welcomed him as a fund-raiser whose secret dealings with Chinese espionage officials have buttressed Republican accusations that China put into effect a plan to use money to influence the 1996 Presidential race.

It was the Democrats from Mr. Chung's party who turned on Mr. Chung, bitterly denouncing him as an untrustworthy witness.

''You've had your 15 minutes, Mr. Chung,'' said Representative Tom Lantos, Democrat of California. ''You are a very minor, insignificant puppet of the Communist regime.''