Giuliana Rancic is reportedly furious at being replaced on 'E! News' by Maria Menounos.
The 40-year-old anchor quit the entertainment show last month after 14 years at the helm but feels the appointment of her archrival is a "major slap in the face".
A source said: "She feels like she brought 'E! News' back to relevance, because it was going to be cancelled at one point . . . to have her archnemesis now anchoring is a major blow."
And Maria, 37, is said to be feeling "a lot of pressure" to be a success on the show.
Another source told the New York Post newspaper's Page Six column: "Maria was hired only because Giuliana was planning to leave. Maria is feeling a lot of pressure to succeed right now, because all of her shows on the network have failed. Execs are nervous and upset about the deal they've inherited."
The programme will reportedly be split into two half-hour shows with four hosts, and Maria will initially only work on one of the programmes while producers establish how well her appointment is faring.
A source said: "It's a test period to see how she works on the news desk, and if ratings continue to decline, the network will have to re-evaluate."
A spokesperson for E! insisted they are "very excited" to have Maria on board.
The representative said: "There is no truth to it being broken up in two half-hour shows. We are very excited to have Maria expand her role on the E! News team -- she is a talented and popular personality across the network."