McDermott, who at the time was the panel's senior Democrat, failed to meet his obligations as a committee leader, said a report released two days after Congress adjourned for the year. The panel took no action other than the report.
"Rep. McDermott's secretive disclosures to the news media ... risked undermining the ethics process regarding" former House Speaker Newt Gingrich, the committee said. It said McDermott's actions "were not consistent with the spirit of the committee's rules."
The ethics complaint stems from a tape recording made by a Florida couple, who gave it to McDermott in January 1997. The tape recorded then-Speaker Gingrich, R-Ga., in a December 1996 conference call with GOP leaders regarding a separate ethics investigation of Gingrich.
McDermott leaked the tape to The Atlanta Journal-Constitution and The New York Times, which published stories on the case in January 1997.
Gingrich, who was heard on the call telling House Republicans how to react to the ethics charges against him, was later fined $300,000 and reprimanded by the House.
A three-judge panel of the U.S. Circuit Court of Appeals for the District of Columbia ruled against McDermott in a related civil case in March. The 2-1 opinion upheld a lower court ruling that McDermott had violated the rights of Rep. John Boehner, R-Ohio, who was heard on the 1996 call. Boehner, then a Gingrich lieutenant, is now House majority leader.
The full nine-member appeals court vacated the three-judge ruling this spring and heard new arguments in the case in October. A ruling is expected next year.
McDermott, in an e-mail to The Associated Press, said he was pleased the ethics panel had concluded he did not violate overall House rules.
"I am also pleased with the committee's acknowledgment that pending litigation in the federal court will decide the question of law over the First Amendment issues involved," he said.
Because of the pending civil case, McDermott said he would not offer additional comment.
Rep. David Hobson, R-Ohio, a former ethics committee member who filed a complaint against McDermott in November 2004, said he was disappointed the ethics panel did not sanction McDermott.
"I'm not sure this decision reflects well upon the House as a whole or the ethics process," Hobson said.
He said he might change his long-standing support for an internal ethics panel and consider replacing it with an independent inspector general to investigate House members.