The '80s popstar told the Sunday People that "the boss" is very worried about the programme and thinks the only way of saving it is to rejoin the panel.
Sinitta said: "This has been the worst series ever and Simon wants to come back. He has so much affection for the UK show, he is the boss and he wants to be back on UK TV.
"I think there have been moments when Simon has thought, 'Oh my God, what is going on?' He is a control freak. He has his ways and his methods to his madness.
"In my view it has been the worst show yet in terms of watchability. There has been some great talent, some great singers but there is something missing.
"Simon says X Factor is his first baby. He worries about the show and there is a lot for him to worry about at the moment."
Sinitta went on to reveal that Cowell thinks the wrong people are going.
"He finds it frustrating," she said. "He doesn't want the whole thing to fall apart."
The SyCo boss tweeted his shock at Ella Henderson's elimination last weekend.
In what was seen as an effort to stop Christopher Maloney winning the show, he encouraged viewers to vote for who they could see as "a star" next year.
The 'So Macho' singer also speculated about who Cowell would replace on the judging panel, saying that he and Gary Barlow are too similar.
"Simon cancels Gary out, so sorry Gary," she said. "They both wrinkle their nose at certain things but Simon's instincts are sharper, Simon's the one who can spot the X factor."
Cowell is currently in LA working on the US version of the programme.
Photo gallery - Motown and ABBA-themed live show:
Copyright: Ken McKay/Thames/Rex Features