Members of six national black political and economic groups have filed legal papers in U.S. District Court here charging that a federal investigation into contracting by the District government is part of a national effort to discredit black leadership.

The legal action was filed late Monday as a "friend of the court" brief in which the organizations said Mayor Marion Barry, officials in his administration and black city contractors are the victims of a "white power structure" that is employing "the longstanding and enormously successful tactic of utilizing the powerful law enforcement agencies to discredit black leadership."

The brief contended that "at each point in our nation's history, when black Americans have attempted to flex their political muscle, white Americans have responded with intimidation, assassination, persecution or prosecution."

The legal papers were filed by the National Black Leadership Roundtable, the National Black Caucus of State Legislators, the National Black Caucus of Local Elected Officials, the National Conference of Black Mayors and the National Association of Black County Officials, and members of the Congressional Black Caucus.

"A number of black groups and, we hope, eventually other groups will see this as a threat to civil liberties," said Herbert O. Reid Sr., legal counsel to Barry. The mayor, in a suit pending before Chief U.S. District Judge Aubrey E. Robinson Jr., has accused federal prosecutors of misconduct in allegedly leaking information about the contracting investigation to the news media.

U.S. Attorney Joseph E. DiGenova, whose office declined to comment on the latest court filings, has said in previous legal papers that Barry has failed to show that the U.S. attorney's office has been the source of any leaks about the investigation.

On May 22, diGenova's office announced the end of a 17-month undercover phase of an investigation into the awarding of District government contracts. A number of city agencies and private businesses were served with subpoenas for documents and search warrants were executed at two businesses and two residences.

No one has been arrested or indicted in the case.

Reid said the support from other political groups "does not mean any tolerance of corruption or wrongdoing, but we just believe that the {proper} process should be followed."

The court papers stated that "many of our members have found themselves . . . the target of governmental investigations, the nature, intricate and confidential details of which were mysteriously leaked to and reported by the press."