U.S. District Chief Judge William B. Bryant yesterday refused to make public the secret two-page report filed with him by the federal grand jury that began investigating South Korean influence-buying in Congress.

The federal panel filed the report with Bryant Monday at the end of its 18-month term. The Justice Department will continue presenting evidence to a new panel.

In a three-sentence order released yesterday. Bryant said only that "pertinent" legal authority required him to conclude that the document should remain secret.

The Washington Post reported on Monday that sources familiar with the investigation said the grand jury wanted to make critical references to Rep. Edward J. Derwinski, (R-III.).

Members of the grand jury were convinced, sources said, that Derwinski was responsible for informing the South Korean government about the planned defection of one of its intelligence agents to the United States. Prosecutors reportedly told the grand jury that there was not enough evidence to support a criminal indictment of Derwinski.

Derwinski, who consistently has denied he played any role in the defection incident, has called for an investigation into the sources of the Post story. Bryant's ruling yesterday did not discuss that request.

Local and state grand juries often are allowed to filed critical reports on matters they investigate, but the main purpose of a federal grand jury is to determine "probable cause" as to whether a person, has committed a crime.

Sources also told the Post that the grand jury wanted its information about Derwinski forwarded to the House Committee on Standards for Official Conduct for possible disciplinary action. Bryant's order appears to preclude that step.