A secretly taped conversation between Mayor Harold Washington and a municipal sewer worker with political ambitions has surfaced here, leaving the mayor embarrassed and City Hall's feuding factions in a new uproar.

The headline-grabbing episode involves a recording surreptitiously made by a sewer worker seeking to defeat a feisty, Washington-appointed alderman in a special election on the South Side on Tuesday.

The recording discloses no evidence of backroom deals or political impropriety. But in it, Washington makes disparaging remarks about the alderman, Dorothy Tillman. And he speculates about the power of his arch-antagonist, Alderman Edward R. Vrdolyak, to cause the mayor political trouble in his own South Side backyard.

The office seeker, James Burrell, is heard trying to get a promise of a better sewer job from the mayor. He also suggests that if his campaign debts can be covered he might withdraw from the race. The mayor equivocates. The conversation ends with no firm commitments on either side.

Prosecutor Richard M. Daley has launched an investigation, with a Cook County grand jury taking sworn testimony. Illinois' eavesdropping laws are among the toughest in the nation. For a conversation to be recorded legally, everyone involved must consent to it.

Burrell met privately with Washington in the mayor's Hyde Park apartment Jan. 30, ostensibly to discuss Burrell's chances in the election. Burrell says he carried the tape recorder on the advice of a former alderman who is appealing a mail fraud conviction obtained in part on the strength of evidence contained in secret recordings. The convicted alderman, Tyrone Kenner, has denied involvement in the latest taping.

After Kenner's conviction last year, Washington appointed Tillman to fill the seat until Tuesday's special election. Tillman is widely known in Chicago as an outspoken and frequently abrasive community activist.

The Chicago Tribune published excerpts of the Burrell-Washington tape Wednesday, and followed with the complete transcript Thursday, "as a public service." The Tribune turned the tape and a pocket-sized recorder over to Daley. The paper's editors have said they will resist any attempt by the grand jury to question the reporter.

The grand jury questioned Burrell on Friday, and he reportedly invoked the Fifth Amendment, the constitutional guarantee against self-incrimination. The paper also is investigating how the tape "made its way into the camp of Vrdolyak," editor James Squires was quoted as saying Thursday.

The three-hour taped conversation opens with the mayor telling Burrell, "You're looking distinguished." But the conversation quickly becomes a complaint-filled recitation by Burrell against Tillman. The mayor temporizes and philosophizes but has some cutting things to say about his ostensible ally as well.

At different times, Washington calls her "abrasive," a "loser," "insecure" and "too loud." He boasts of his power in the Third Ward, saying, "I put her there. And so far as the [City] Council's concerned, she's cooperating. She's green as grass, but she's cooperating."

Tillman -- who faces eight challengers, including Burrell -- has publicly supported the mayor in this latest flap. They have made several joint appearances, and she has defended him.

But Washington denounced the media in a speech at an inner-city college campus. "I don't have to answer for this," he told an audience of cheering students at The Loop College. "They [the media] don't seem to understand you have the right to your privacy . . . . They can say any darn thing they want . . . . "

Vrdolyak has disavowed any connection with the tape or with Burrell. But in the recorded conversation, Washington worries that Vrdolyak can cause dissent within the Third Ward. Vrdolyak is chairman of the Cook County Democratic Committee and leader of the 29 white aldermen who are a majority in the 50-member City Council and have opposed Washington from the moment he was sworn in.

On the tape, the mayor ruminates with Burrell about the many candidates running against Tillman and says that there is "the risk of just having a whole lot of anger, and upset angry people and friction . . . and that's what Vrdolyak wants.