The alleged victim filed a police report early Sunday morning with the LAPD … claiming he and his friends were sitting behind Miley and her fiance Liam Hemsworth at Beacher’s Madhouse at the Roosevelt Hotel when things got rowdy.

The alleged victim claims he and his friends accidentally bumped into Liam’s chair and the two camps exchanged words … an argument that quickly escalated.

The alleged victim claims Liam got in his face and Miley jumped in the middle to break it up — but not before pushing him away and striking him in the face.  There were no visible injuries.

A witness tells TMZ … he saw the argument but Miley never threw a punch.

Calls to Miley and Liam’s camp were not returned.