The actor came out swinging Tuesday to deny a claim Sharon recently floated on a podcast -- where she alleged late producer Robert Evans told her she should bang Billy to get a better performance out of him in 1993's 'Sliver,' in which she starred opposite Billy.

In response to that, Billy wrote ... "Not sure why Sharon Stone keep talking about me all these years later? Does she still have a crush on me or is she still hurt after all these years because I shunned her advances?"

Billy goes on to claim that Sharon confided with her friend, Janice Dickinson, that she was going to "make him fall so hard for me, it's gonna make his head spin." Basically, he's making it seem like Sharon actually wanted to get with him while they were shooting.

Billy makes another startling allegation, writing ... "The story of the meeting I had with Bob Evans imploring him allow me to choreograph the final sex scene in the photo below so I wouldn't have to kiss Sharon is absolute legend." He teases spilling some tea one day.

Sharon coming out with this story follows years of her teasing being ready to reveal the identity of a producer she says was scummy -- and now, she's naming Evans as that guy.

Sharon went on to explain that she'd been told the acting issues with the movie at the time were being blamed on her ... all because she refused to sleep with Billy, which she says Evans apparently thought would make their chemistry better and "save" the flick.

She says she'd suggested other actors besides Billy -- like Michael Douglas -- whom she says she considers a professional ... so yeah, she's kinda trashing BB here too.