Khloe Kardashian Rips Ex-Stepmoms: 'You Are Disgusting'

Khloe Kardashian is lashing out at her former step-mothers -- claiming the women should be "ashamed" for telling a tabloid magazine that Robert Kardashian isn't her biological father.

Khloe's fury is directed at Jan Ashley and Ellen Kardashian -- who were each married to Robert after he split from Kris Jenner. Both recently claimed Robert privately revealed to them that Khloe was fathered by another man.

Now, Khloe is firing back on Twitter ... saying, "The audacity you have to mention my father’s name like this! Should be ashamed of urself! I let a lot of things slide but this one is really low… YOU ARE DISGUSTING! (yes you know who YOU are)."