RICHMOND, SEPT. 24 -- The private detective hired to investigate the personal life of U.S. Sen. Charles S. Robb (D-Va.) said today that his client was a Richmond area physician, not the state Republican Party as Robb has charged.

Billy A. Franklin, the Virginia Beach detective whose investigation two summers ago led to a Robb campaign complaint to the Federal Election Commission, confirmed an earlier Washington Post report that his client was a physician who has been active in Republican Party affairs.

Robb and his aides released documents over the weekend contending that Franklin has been the point man for an "array of unfounded rumors" about Robb that have been sponsored by GOP officials, including the Republican U.S. attorney for Eastern Virginia, Henry E. Hudson.

Franklin is writing a book about his two-year investigation into reports that Robb, while governor from 1982 to 1986, knew and socialized with cocaine users in Virginia Beach. Franklin said today that his sole employer for the Robb investigation was Louis H. Williams, an obstetrician-gynecologist who once unsuccessfully sought the Republican nomination for Congress from the Richmond area.

Williams's secretary said today that Williams is vacationing out of the country and could not be reached for comment.

Hudson, state Republican Chairman Donald W. Huffman and GOP Executive Secretary Joe Elton all denied any association with Franklin, a private detective and lawyer who, before his investigation of Robb, was best known as a lie detector expert.

Although Elton said he is convinced that no party official contributed money to Franklin's efforts, Williams reportedly solicited money from Republicans around the state to help finance Franklin.

David K. McCloud, Robb's chief of staff, said today that reviving the long-dormant story about Franklin's investigation is a risk.

On the one hand, the action would refocus public attention on allegations that Robb was present at parties where cocaine was used, allegations Robb vehemently denies.

On the other hand, McCloud said, it is necessary to "put in context" the impending release of information gathered by Franklin, which he has said will be revealed in a manuscript, tentatively titled, "Tough Enough."

"It's less damage control than simple fairness," McCloud said.

Franklin said Williams approached him in the summer of 1988, when Robb was running for Senate, and asked him to look into rumors that Robb was involved with drug users during frequent visits to Virginia Beach.

Williams, Franklin recalled, told him that if the rumors were true, Williams did not want to see Robb go on to be elected president or vice president. Franklin said Williams expected Robb to easily win the Senate race against a relatively unknown Republican, Maurice A. Dawkins. Robb won with 71 percent of the vote, but was dogged throughout the campaign by suggestions of misbehavior.

At the time, a federal grand jury in Norfolk was investigating drug use in the Tidewater area. The grand jury returned a dozen indictments and offered immunity to as many others, including several acquaintances of Robb's, according to sources.

Williams has been named in previous news stories as Franklin's employer, but Williams has said he did not help defray the cost of Franklin's investigation and Franklin had declined to publicly identify his client. Franklin said today that Williams released him from a promise of anonymity earlier this year.

Franklin was ordered by a federal court to identify the client after Robb complained to the Federal Election Commission that Franklin's investigation was part of a Republican effort. Robb contended that payments to Franklin would be reportable as campaign contributions to Dawkins.

Faced with the court order, Franklin said Williams agreed to let his name be revealed and pick up the legal fees for defending Franklin before the election commission. Franklin had identified Williams to the commission, but not to the public, he said.

Because Williams was unable to raise enough money to pay his fee, which including expenses exceeded $100,000, Franklin said, Williams agreed to allow Franklin to retain the information gained during his inquiry. That information forms the basis for Franklin's proposed book, he said.