Their kids, Junior, eight, and six-year-old Princess, have been spending time with Peter, his fiancée Emily Macdonagh and their new sister Amelia, who was born in January.
But according to Katie, she hasn't heard from either of her kids – and she took to Twitter on Saturday to vent her fury.
She told her 1.81 million followers: "disgusting,haven't heard from my children for 11 days no tex no missed calls no messages and people wonder why I don't have good word to say."
The latest blast follows a December tweet in which Katie - who has two other children, Harvey, 11, and five-month-old Jett - branded singer Peter with the hashtag #fakefamilyman.
It topped off a bad weekend for the model-turned-author, who also revealed how a designer handbag had been stolen from her car after a night out in Horsham, West Sussex.
She tweeted: "In Horsham someone smashed my window stole my bag with all valuables in! Pure scum low life's."
She also issued an appeal for the safe return of her cream Louis Vuitton bag and reported the theft to the police.
Katie added: "Anyone who is given a cream round barrel louis v bag and black louis v card holder in Horsham it's mine! Also my valuables inside."
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