D.C. businessman John B. Clyburn, whose business offices were searched May 22 as part of the federal probe into city contracting, asked a federal judge yesterday to declare the search illegal and prohibit prosecutors from using any of the seized items as evidence against Clyburn.

In a petition filed yesterday, Clyburn's attorney, Thomas R. Dyson, also asked that all property seized from Clyburn's businesses, Decision Information Systems Inc. and the Data Processing Institute, be returned and that the government be required to make public the affidavit that was filed to obtain the two search warrants.

Clyburn, who recently sold his interest in DISC, is a close friend of Mayor Marion Barry's and is a key figure in the contracting investigation and the separate probe into the alleged payment of hush money to keep convicted cocaine dealer Karen K. Johnson from testifying before an earlier federal grand jury looking into alleged drug use by Barry and others.

"Mr. Clyburn has been held up to the public obloquy and villified by the media, press, radio and TV," Dyson said in the court papers. "Every sort of rumor, innuendo and speculation has been presented to the public.

Dyson said Clyburn "is being driven to financial ruin, and the hardship on his family is immense. Yet he cannot defend himself for there is nothing to defend."

The request by Clyburn is one of several legal challenges brought by figures in the broad corruption investigation -- including a highly publicized suit by Barry -- but it is the first that has specifically asked for release of the search warrant affidavit.

Sources say that the affidavit provides a very specific description of the evidence the government obtained during its 17-month undercover FBI investigation and provides an overview of the entire probe. The affidavit has remained sealed, under court order, although the lists of the items seized during the searches has been made public.

Dyson said "it is unheard of in this jurisdiction" for the warrant to remain sealed.

The papers also seek affidavits in support of court-ordered wiretaps or bugs that might have been used to overhear conversations by Clyburn. It is believed that the government obtained wiretaps for Clyburn's office telephone and possibly placed an electronic bug in his office.

The search warrants, which contained details about locations and the types of documents to be seized, listed only the criminal violations prosecutors are investigating. The possible crimes listed in the search warrants for Clyburn's business included obstruction of justice, racketeering, bribery and extortion.

In addition to the searches at the two businesses, FBI agents searched the offices of D.C. developer T. Conrad Monts and the homes of Johnson and David E. Rivers, a top aide to Barry.

A spokesman for the U.S. attorney's office had no comment on Clyburn's motion, which apparently will go to Chief U.S. District Judge Aubrey E. Robinson Jr., because the investigation is still before the grand jury.