D.C. Mayor Marion Barry offered yesterday what he said was evidence bolstering his repeated assertion that federal authorities engage in leaking information to the news media about investigations involving his friends and associates.

Barry, in papers filed in U.S. District Court here, claimed that in recent depositions in a libel suit, reporters for The Washington Times stated that a federal prosecutor and an FBI agent provided information for a story about the 1983 drug-related death of Joann T. Medina.

The court action by Barry was the latest in a legal dispute between U.S. Attorney Joseph E. diGenova and the mayor, who has charged that the prosecutor's office has sought to undermine his administration by leaking information to the media about a wide-ranging grand jury probe of D.C. government contracting.

An attorney for The Washington Times said that Barry had "taken out of context" statements by Times reporters and that the statements had no relevance to the contracting investigation. The depositions were taken in December in connection with a suit against the Times by Washington businessman John B. Clyburn.

At issue in Barry's claim against diGenova is whether federal authorities have violated a court prohibition against divulging activities of a grand jury. It was unclear from the papers filed by Barry yesterday what role the unnamed FBI agent and federal prosecutor had played in the earlier stories published by the Times, or whether they had provided information from secret grand jury proceedings.

Barry filed suit against diGenova last month to block what he said were leaks about the current contracting probe. DiGenova responded last week in his own filing that Barry has been unable to show that federal prosecutors have been the source of information for news reports, and asked that Chief Judge Aubrey E. Robinson Jr. throw out Barry's suit.

Barry said yesterday that news leaks are continuing and that the prosecutor's alleged improper handling of the investigation has created an atmosphere in which city officials contend "firms are reluctant to do business with the District of Columbia for fear of being implicated or investigated by the United States attorney for charges of corruption."

Robinson has not indicated when he would rule on the issue. A spokesman for diGenova's office declined comment yesterday on Barry's latest court filing.

Barry, contending that actions by authorities in the Medina case provide evidence of improper cooperation between federal authorities and the news media, referred to a deposition of Washington Times reporter Jerry Seper. The Barry filing quoted Seper as saying, "Oftentimes law enforcement agencies say that when you have articles in the paper sometimes it shakes the trees, other people will come out and start talking to them."

Barry, in his filing yesterday, said, "As desirable an investigative tool that this practice might be, it, like the rack and screw and the torture chamber, is prohibited in this free democracy."

Clyburn, a close personal friend of Barry's and a central figure in the government contracting investigation, filed a $25 million libel suit against the Times last year after the newspaper published a series of stories linking the death of Medina, a longtime friend of Clyburn's, with a drug counseling contract held by Clyburn's company.

No one has been arrested or indicted in the contracting probe that became public on May 22 when diGenova announced the end of a 17-month undercover phase of the investigation in which an FBI agent posed as a city contractor. On that day, authorities issued 15 subpoenas to private firms and government agencies and executed four search warrants of firms and private homes to obtain documents related to the probe.

Barry, who initially said the probe was not affecting city government, has since complained that the investigation has cast a shadow over the entire operation of city government. Barry and other city officials have called on diGenova to move quickly to obtain indictments or end the probe.

In yesterday's filing, Raymond A. Lambert, director of the Department of Administrative Services, said that the probe has had a chilling effect on firms that want to do business with the city.

Lambert said in an affidavit filed with the court papers that participation in bids for city projects has "fallen sharply" in recent weeks. He added, "All of the . . . contractors being targeted are minority companies, even though roughly two-thirds of {city} contractors are nonminority companies. These statistics have grave implications for the minority business community."

Barry and Lambert appeared yesterday at a city-sponsored luncheon for minority business owners held at the Phillips Flagship restaurant in Southwest Washington. Barry did not mention his latest court action, but told about 40 minority business representatives that a government program to set aside work for minority firms "is under extreme attack."