Doubts grew yesterday about the existence of "sex tapes" purportedly showing murdered model Vicki Morgan and government officials after Hustler magazine publisher Larry Flynt said a lawyer offered to sell them for $1 million but then reneged on the deal.

Attorney Robert K. Steinberg reported Tuesday that the tapes had been stolen from his office. But Flynt said Steinberg made a deal to sell the tapes at 9 a.m. yesterday.

"I told him if, in fact, the tapes existed, I would pay him $1 million, no questions asked," Flynt told the Associated Press. "He said, 'We've got a deal.' I made an 11:30 a.m. appointment at my house with him. He never showed up."

In a telephone interview with a Los Angeles city news service, Steinberg was quoted as saying, "Mr. Flynt is a liar."

"I have never met him," Steinberg said. " . . . I invite him to take a polygraph test on that issue . . . if he talked to me and offered me $1 million for those tapes."

Flynt's spokesman, Robert David, told reporters yesterday morning that the publisher had obtained the tapes and would identify the people on them. But Flynt said David had misunderstood a message he left with his secretary about the impending deal with Steinberg.