HONOLULU (AP) _ Former Rep. Cec Heftel of Hawaii says he will announce his preference for governor once he finds out who smeared him during the Democratic gubernatorial primary race.

Heftel held a 21-point lead over his closest rival, Lt. Gov. John Waihee, in a Honolulu Advertiser poll published six days before the Sept. 20 primary election. Waihee defeated Heftel 45 percent to 36 percent.

Heftel blamed his primary race loss on a smear campaign, which he said was orchestrated by either Waihee or Republican gubernatorial nominee D.G. Anderson. They have denied it.

Heftel was particularly upset by the anonymous mailing, two days before the primary, of a confidential state report containing allegations about his personal life.

The 1983 report was made to the state Investigations and Narcotics Control office by an unidentified informant. Copies of the report were sent anonymously to news media representatives, who did not publish or broadcast it, and other gubernatorial candidates, who did not mention it.

Nevertheless, Heftel believes the report had an impact. The state attorney general's office is investigating.

During an emotional speech to about 500 supporters at a party last Sunday to mark his 62nd birthday, Heftel said the report alleged ''that I was a homosexual; that I had sex relations with children; that I, in particular, had homosexual relations with blacks; that I was a drug addict; and that I was an alcoholic.''

Heftel, a Mormon, said he doesn't drink or smoke, and doesn't even take aspirin.

As for his sexual preferences, he said, ''I've got to be the squarest, straightest person sexually that ever existed.''

Further, Heftel said he was the target of a whisper campaign consisting of unfounded rumors.

''These rumors included that I'm a racist, that I hate Japanese (the second-largest ethnic group in Hawaii), that I want local people to lose their jobs; that I'm an alcoholic; that I'm corrupt; that only haoles (Caucasians) can work for me; and that I get rich off of politics.''

City Prosecutor Charles Marsland has dismissed the report, saying there is no evidence to support the allegations made against Heftel. The report was forwarded to Marsland's office because a portion of it concerned people who had been prosecuted earlier by his office.

''Ultimately, as far as we were concerned, it (the contents of the report) proved unreliable,'' said City Deputy Prosecutor Peter Carlisle.

Anderson joined Heftel in calling for an independent investigation into the release of the state report. Heftel said he doubts the Ariyoshi administration's investigation of the report will be completed before the Nov. 4 election. He said he hopes to complete his own investigation before the election, and will make the results public.

On Wednesday, the original report, copies of the report and the envelopes used to mail them were given to the FBI for analysis, said Deputy Attorney General Keith Kaneshiro, who is leading the state's investigation. Results were expected in about 10 days, he said.

Kaneshiro said it was not unusual for the report to remain on file even though its contents had been dismissed by prosecutors.

While Heftel blamed the alleged smear campaign for his primary loss, political observers said Waihee mounted a strong grassroots campaign, particularly in the final weeks.

''I believe this election was won by the Waihee wave and not a Heftel smear,'' Waihee said.

Anderson said Heftel simply ''ran into a buzz saw ... that's been controlling this state for 30 years.'' Waihee ran with the strong support of Ariyoshi and most other Democratic Party leaders.

Patsy Mink, who finished third in the Democratic gubernatorial race, said she thought Heftel lost because of media advertisements attacking Heftel's congressional voting and attendance records.

She also said the report was circulated too late to affect the voting, and noted that the contents of the report were not reported by any media.

Heftel agreed that the great majority of voters did not hear the smear charges, but said, ''The attacks were cleverly aimed to hit where they would do the most damage, where they would create enough doubt among enough voters to affect the outcome of the election.''

Others said Heftel, a millionaire, was hurt by campaign spending reports released late in the campaign which showed that he had spent $2.2 million in his campaign, including $1.4 million of his own money. Heftel's spending was more than three times that of Waihee.

Heftel said Tuesday that he would not launch a write-in campaign.