A fifth woman accusing Smokey Robinson of sexual battery has officially come forward and filed a police report … TMZ has learned.

Law enforcement sources tell us the woman spoke with a deputy last Wednesday at the Los Angeles County Sheriff’s Department’s Malibu/Lost Hills station, where she formally reported her allegations against the Motown singer.

We’re told all five accusers have filed reports with LASD.

As we first reported, Robinson became the subject of a criminal investigation by the department’s Special Victims Bureau in May, after four women came forward accusing him of sexual assault.

Robinson’s attorney, Christopher Frost tells TMZ … “It’s not surprising to us that in the context of very public allegations by the four interconnected Jane Does and their shared attorneys, no matter how untrue, news like this might emerge. It’s one of the risks of being a celebrity, that others will take the same approach.”

He continues, “Our focus is on exposing the falsity of the Doe lawsuit, where the Does and their lawyers have taken a hit and run approach — making allegations against a beloved 85-year-old cultural icon and subsequently refusing to reveal their identities or unequivocally sit for a deposition, where the truth can actually be determined.”

Previously Frost told us the police reports were only filed after the women filed a $50 million civil lawsuit against Smokey … and he suggested it was a strategic move, not a legitimate claim. He said Robinson welcomed the investigation which is is ongoing.