The Justice Department's inquiry into whether an independent counsel should be appointed to investigate conflict-of-interest allegations involving former Supreme Court nominee Douglas H. Ginsburg has moved into the phase of a formal preliminary investigation, according to department sources.

The independent counsel law calls for a preliminary investigation to be launched whenever the attorney general receives information "sufficient to constitute grounds to investigate" that the official has committed a crime.

It was previously reported that the Justice Department's Office of Public Integrity had begun a "threshold inquiry" into whether an independent counsel should be appointed to investigate Ginsburg's handling of various cable television matters as an assistant attorney general in charge of the Justice Department's antitrust division. The preliminary investigation represents the next step in deciding whether an independent counsel is warranted.

The inquiry was broadened into a preliminary investigation last month, sources said.

Ginsburg, a judge on the federal appeals court here, was nominated for the Supreme Court Oct. 29 after the defeat of Judge Robert H. Bork. He withdrew nine days later after admitting that he had smoked marijuana while a professor at Harvard Law School and following reports of a potential conflict of interest in cable matters.

After a preliminary investigation is begun, the attorney general has 90 days either to ask a special three-judge court to appoint an independent counsel or to report to the court that "there are no reasonable grounds to believe that further investigation or prosecution is warranted."

In Ginsburg's case, the 90 days would elapse sometime in late February.

Ginsburg did not respond to a request for comment. Justice Department spokesman John Russell also declined to comment.

The investigation concerns Ginsburg's actions on cable television matters while at the antitrust division from 1985 until November 1986, sources said. On his financial disclosure reports at the time, he listed an investment of almost $140,000 in Rogers Cablesystems, a Toronto-based cable television company that has operations in the United States.

Ginsburg handled a number of Justice Department matters involving the cable television industry. He sided with the cable industry in arguing against the "must carry" regulations -- proposed Federal Communications Commission rules to require cable operators to carry certain channels.

He also filed comments with the FCC opposing proposed restrictions on multiple ownership of cable systems and supervised an antitrust division investigation into whether cable companies conspired to force pay cable channels to scramble their signals so that satellite dish owners could not intercept them.

In addition, Ginsburg said he was a "principal participant" in drafting a Supreme Court brief in 1986 arguing that cable operators are protected by the First Amendment.

Federal law makes it a crime for government officials to participate "personally and substantially" through "decision, approval, disapproval, recommendation, the rendering of advice, investigation or otherwise" in any maters in which they have a financial interest. Officials may handle such matters if they receive a written determination that their interest "is not so substantial as to be deemed likely to affect {their} integrity."

In Ginsburg's case, Justice spokesman Terry Eastland said at the time of the disclosures that Ginsburg "after consultation with staff . . .determined that Rogers would not be affected financially by the Preferred Communications proceeding in the Supreme Court."

Eastland said the company was not a subject of the antitrust scrambling probe and that although Ginsburg was "informed of the position taken" in the FCC filings, he "was as a matter of course not involved in the development or articulation of the antitrust division's position."