RICHMOND, SEPT. 27 -- Reports that a private detective is writing a book about the personal life of Sen. Charles S. Robb (D-Va.) may have breathed life into a two-year-old investigation by the Federal Election Commission about whether GOP officials violated campaign laws by hiring the investigator.

A complaint to the FEC initiated by the Robb campaign during his 1988 campaign for the Senate alleges that GOP state Chairman Donald Huffman and other party officials financed the investigation by Virginia Beach investigator Billy A. Franklin, whose book reportedly provides new information about Robb's behavior during visits to Virginia Beach when he was governor from 1982 to 1986.

Robb has steadfastly denied reports of impropriety, most recently in an article in the October edition of Regardie's magazine. The article quoted Franklin as saying that he has "several new witnesses to Robb's alleged sexploits plus witnesses who saw Robb surrounded by cocaine."

In a written response to the magazine, Robb's chief of staff, David K. McCloud, said that Robb "has unequivocally denied . . . that he has ever, in his lifetime, been associated in any way, shape or form with illegal drugs . . . . As naive as it sounds, to this day he does not believe he has ever seen illegal drugs except in photographs or on TV."

Robb said essentially the same thing in 1988 when The Washington Post and Virginia newspapers ran stories about reports of misbehavior.

Franklin found, according to Regardie's, that Robb "partied with people {who not only used drugs} copiously {but} favored the company of young women, in some cases women just to the legal side of jailbait."

McCloud responded to that by writing that "Senator Robb has said repeatedly that the only woman he has loved, either emotionally or physically, since he's been married, is his wife, Lynda."

In the FEC case, Robb contends that the GOP should have reported any payments to Franklin as campaign contributions to his opponent, little-known Republican Maurice A. Dawkins. Robb won with 71 percent of the vote.

Huffman and GOP Executive Secretary Joe Elton maintain that the party was not involved in employing Franklin. But several Republicans say they were asked to help pay for the effort, which reportedly was the brainchild of a Richmond obstetrician, Lewis H. Williams.

Franklin told The Post on Monday that Williams was his sole employer. Williams is out of the country and could not be reached.

Furthermore, GOP sources said, no one seriously thought that Dawkins, of Arlington, had a chance of beating the former governor. The purpose of the investigation, they say, was to determine the truth about reports that Robb may have attended parties in the resort city at which cocaine was present.

Elton said today that he would "like to tell my side of the story, and if it weren't for restrictions placed on me by FEC I would, and I intend to seek their favorable opinion that I can go ahead and do so."

One Republican who was interviewed by the FEC this year said today that FEC investigators are returning to Richmond on Friday to re-interview individuals they contacted in their probe.

Sharon Snyder, a spokeswoman for the FEC, declined to comment on the status of the investigation.

Elton reiterated his contention that "the Republican Party did not give one thin dime for the support of the investigation." He said Robb's complaint "is specious on two counts." Not only did the party not contribute to Franklin's effort, Elton said, but "it is my understanding that the investigation wasn't undertaken to affect the 1988 election. It was simply to find out the truth. And we haven't heard the truth yet."