JOIN USMultnomah County District Attorney Michael Schrunk said in an e-mailed statement that he agreed with the recommendation by investigators that there be no criminal prosecution.
Investigators found that the red-headed massage therapist Molly Hagerty, 54, had contradicted herself, that her clothes contained no semen and that she had been paid by a notorious tabloid newspaper for her story.
In a memorandum to Schrunk recommending the case be dropped, one of his deputies, Don Rees, cited "contradictory evidence, conflicting witness statements, credibility issues, lack of forensic evidence and denials by Gore".
Police in the city of Portland had reopened the case several weeks ago. Hagerty had reportedly accused Gore of sexually assaulting her in a Portland hotel in 2006, but the investigation was dropped for lack of evidence.
It was reopened after his accuser gave an interview published in June in the tabloid National Enquirer.
In the interview, she called Gore a "pervert and sexual predator" for requesting a "happy ending" at the end of a massage session. She claimed that he sexually assaulted and groped her when she refused.
Police investigators found discrepancies within Hagerty's statements, which variously said she was terrified yet had told Gore to "dream of redheaded women", according to Rees's memorandum to the District Attorney.
Hagerty failed to provide medical records and other documents she claimed would prove her case, and failed a lie detector test. She had been paid by the National Enquirer for the story, Rees noted. And forensic testing of pants she gave to investigators failed to show the presence of semen.
Gore and wife Tipper announced in June that they were separating after 40 years of marriage. Gore has long been a champion for stopping global warming, and won the Nobel Peace Prize for his effort in 2007.