Robert Kardashian's widow, Ellen Kardashian, has filed a defamation lawsuit against Kim, Kourtney, Khloe and Rob Kardashian and momager Kris Jenner for defamation and intentional infliction of emotional distress -- adding Ryan Seacrest Productions and Keeping Up With The Kardashians producers to the lawsuit, as Breaking Celebrity News exclusively reported she would.

According to the court docs, Ellen claims a private detective hired by the Kardashians contacted her to entice Kardashian's widow to "buy damaging information about herself and Jenner that he had obtained through investigations which were purportedly ordered by Robert Kardashian prior to his death...

"When Ellen refused to engage in such a discussion or transaction, Jake (private investigator) abruptly and menacingly terminated the dialogue by threatening to turn the information over to the Kardashians."

COURT DOCUMENTS: Kardashian Ex-Stepmom Adds Ryan Seacrest & E! Producers To Lawsuit

The lawsuit alleges that "after the alleged attempt to entrap Ellen into the drama of their scripted