The 40-year-old TV personality is said to be “furious” with her former partner – with whom she has children Bunny, four, and Jett, five – and is refusing to speak with him after he said he was never able to compete with Katie’s first husband Peter, who is the father of her children Princess, 11, and Junior, 13.
A source told The Sun Online: “Katie’s furious with Kieran and doesn’t understand why he did it.
“She thought they were supposed to try and get along for the sake of the kids, and then he goes and does this.
“She’s embarrassed about what he said about Pete and wishes he’d kept his trap shut.
“She’s told him to speak to her through lawyers if he has anything to say to her. She’s absolutely fuming with him.”
Kieran, 32, recently blasted the former glamour model in an interview, claiming that if it wasn’t for Katie’s “celeb” lifestyle” she would still be with the pop star.
He explained: “She always said if it wasn’t for her celeb lifestyle, the reality shows and stuff, her and Peter probably would’ve lasted. He was the love of her life and no on can compete with that.
“There’s always someone else to blame. How many more years can she blame things on her and Pete not working out? I’ve probably got it for another five of 10 years.”
Katie also has son Harvey, 16, from a relationship with soccer star Dwight Yorke.
And Kieran has admitted to being upset that the teenager is already calling Kris Boyson – Katie’s new partner – “Daddy”.
He said: “The thing that saddened me most is that when I was still living in the house, he referred to Kris as ‘Daddy Kris’.”