Kim Kardashian West doesn't think Caitlyn Jenner is ''a good person''.

The 36-year-old beauty and her famous family have been feuding with her former step-father - who was previously known as Bruce Jenner - ever since she released her memoir 'Secrets of My Life', which seemingly slammed her relationship with her ex-wife Kris Jenner.

And in a new promotional clip for the upcoming season of 'Keeping Up with the Kardashians', Kim hits out at the 67-year-old television personality for ''lying'' about her late father Robert Kardashian within her book.

In the clip - which was filmed before Caitlyn's memoir was released - Kim is speaking to her sisters Khloe and Kourtney Kardashian about an email she received regarding the book.

She said: ''It says in Caitlyn's book, 'Robert Kardashian knew O.J. Simpson was guilty, but joined the defence team to get back at his remarried ex. Robert told Caitlyn in secret after the O.J. murder trial that he believed his friend was guilty.'''

And when her siblings reacted in shock, Kim continued: ''Dad so believed in him. It is so shady that Caitlyn came over and gave me the book, and then on the phone she said, 'Well, the final version has a few more things in it, but don't worry, it's nothing about you.' So, she lied to me, because that is about me, if it's about our dad.

''I have always had Caitlyn's back. But she is a liar. She is not a good person.''

Speaking to the camera alongside Khloe, 33, after the scene, Kim - who has daughter North, four, and son Saint, 21 months, with her husband Kanye West - admits she's incredibly protective of her late father.

She said: ''My relationship with Caitlyn was strained. I was just trying to just be respectful. But if you talk about my dad, I will cut you.''