Katherine Jackson -- Guardianship Ruling 'Based On Lies'

Katherine Jackson is challenging the court ruling that temporarily stripped her of guardianship of Michael Jackson's children -- and claiming she never wanted TJ Jackson to step into the role ... despite court documents stating otherwise.

In a taped segment for ABC's "Nightline" ... Katherine read prepared comments from a notebook, and said -- "Their ruling in court today was about the guardianship, and I think it was based on a bunch of lies. But I have a good idea who's doing that ... who's behind it."

Katherine went on to say she spoke to TJ last night and "told him it wasn't necessary for him to go down and sign up for guardianship, but I don't know who instructed him to do that ... 'cause he wanted me to come home before that happened."

It's a strange statement because Katherine seems to be acknowledging she knew TJ was going to file for guardianship ... but not before she got home.

In fact, as we reported earlier, TJ stated in court docs that Katherine "supported" him taking steps to protect Michael's kids.

The whole TV segment seemed almost like a hostage situation as Katherine was surrounded by Janet, Jermaine, Rebbie, Rebbie's daughter and, for some reason, the marketing director for the Tucson spa where Katherine's been for more than a week. A local news reporter was in the room, but was not allowed to ask questions.

As for leaving Prince, Paris, and Blanket alone in L.A. -- Katherine claimed she left instructions about who was to take care of them while she was gone ... though she didn't name anyone specifically.