Charles Manson will NOT be glorified in porn … so vows the sister of Sharon Tate.

Debra Tate is incensed over the impending casting of “Manson Family XXX” … a porn parody of the twisted Manson family murder spree that rocked L.A. in 1969.

Adult film director Will Ryder — whose credits include “Not The Wizard of Oz XXX” — will cast Susan Atkins, Patricia Krenwinkel, Leslie Van Houten, Linda Kasabian, Charles “Tex” Watson, and others.  Manson is the central figure who has sex with all of them.

Debra Tate calls it the lowest of lows … vowing to sic her lawyers on producers if they dare use Sharon’s name or likeness.

Problem is, it’s parody so she’s flat out of luck.