Allred said she filed the suit on behalf of her client, Irene McCormack Jackson, U-T San Diego reported.
McCormack Jackson is the first woman to publicly accuse Filner of sexual harassment.
"Irene is that woman," Allred said at a downtown news conference with her client by her side.
Allred said McCormack Jackson had been held in the "Filner headlock" and was "dragged around like a rag doll."
Filner also allegedly said he wanted to marry McCormack Jackson.
Filner, 70, has refused to resign from the office he has held for seven months. He has apologized for behaving crassly toward women and promised to apologize to any women he may have offended.