Mayoral legal counsel Herbert O. Reid Sr. has stepped up his investigation of Jose Gutierrez's handling of the D.C. Department of Administrative Services, retaining a full-time staff assistant and gathering documents to determine whether there was any wrongdoing in the city's awarding of contracts.

Mayor Marion Barry ordered the investigation a week ago, shortly after Gutierrez publicly accused City Administrator Thomas Downs of attempting to influence the awarding of contracts for political reasons.

Gutierrez, former director of administrative services who was demoted to a low-ranking post in the planning office, contends that Barry ordered the investigation to try to discredit him and has ignored his complaints about Downs.

Reid confirmed yesterday that he has asked some present and former department officials, including Barry K. Campbell, former acting head of the Buildings Management Administration, to gather and analyze pertinent documents for him.

Campbell, a former aide to the mayor who was assigned to the Department of Administrative Services in April 1984, later was placed on five days of administrative leave by Gutierrez because of unsatisfactory performance and discourteous behavior to a supervisor.

Campbell subsequently was reassigned to the city administrator's office, where he now works. Yesterday, Gutierrez voiced concern that Reid is relying on information from an employe of Downs' office who has had differences with Gutierrez.

"They [the administration] just want to do a report and charge me with something," Gutierrez said. "Their intent, once it's done, is to transmit the report to the U.S. attorney's office. What they're trying to do is destroy my credibility."

Reid said yesterday that he intends to pursue all leads and that nobody, including Downs, is immune from investigation.

"I hope he . . . [will] supply information and help interpret files," Reid said. "I've asked a whole lot of people to do that."

Campbell said yesterday that he was merely responding to questions posed to him by Reid, and saw nothing improper in his role.

Reid said that he has retained Marlene Johnson, a former deputy legal counsel, to assist him in the investigation.

Asked whether his final report would be sent on to the U.S. attorney's office for review, as Gutierrez predicted, Reid replied: "It may neccesitate somebody else looking at it."

Barry declined to comment yesterday on Gutierrez's allegations that the mayor is attempting to discredit him because he went public with his complaints about the administration.

"I'm not discussing anything else about Gutierrez," Barry said, following a press conference on the Southwest waterfront to announce plans for the District's Potomac Riverfest '85. "I have more important things to do."