Senate President Melvin A. Steinberg said today he will name a special investigative committee with subpoena power to probe allegations of promotional abuses in the state police department if a report by the attorney general into the charges is not given to the legislature.

Attorney General Stephen H. Sachs is nearing completion of a four-month probe into allegations that top state police officials manipulated the agency's promotional system by altering performance ratings. Sachs is expected to turn over the results of his investigation to Gov. Harry Hughes and the state police superintendent early next week.

Reports indicate that the Sachs report will be a scathing indictment of state police promotional practices with indications of scant improvement since his office conducted a similar investigation in 1981.

Hughes indicated at his regular weekly news conference today that he would not release the report. He said that decision would not be made until after he has seen the report, but that "normal procedure is that you do not release investigative reports because the success of investigation oftentimes is the confidentiality of the investigation."

Steinberg (D-Baltimore County), arguing that the legislature must have access to the report if it is to consider legislation to correct problems in the state police personnel system, has had a resolution drafted that would establish a Senate investigating committee. Steinberg said he will ask the Senate to approve the resolution if Hughes does not provide the Sachs report to the General Assembly leadership or if the legislature, after reviewing the report, finds it needs more information.

"I believe the president of the Senate and the speaker of the House are two officials who should have the benefit of that information," said Steinberg. "We may need legislation to set up a promotional system that elevates the best, most qualified people. If the current system is subject to abuses, we have to do something about it."

The last time the Senate convened a special investigating committee was in 1975, when it probed allegations that Baltimore Police Commissioner Donald Pomerleau had used police officers to conduct improper surveillance in the Baltimore black community.

Sachs' investigation began last fall after some members of the Maryland State Police charged that a top-ranking official, Lt. Col William T. Gerwig, had tampered with promotional scores.

Gerwig, citing the law enforcement officers' bill of rights, which holds that only police officers may investigate other officers, has sought a court injunction to prevent the attorney general's office from questioning him about the alleged incidents. A hearing on his motion has been set for March 1 in Baltimore County Circuit Court.