The pair had a brief relationship in 2002 and split shortly after Katie fell pregnant with son Harvey Price, who is now 18.
The teenager suffers from multiple disabilities, including autism, partial blindness and a condition called Prader-Willi Syndrome which has seen his weight balloon to almost 29 stone.
Former Manchester United forward Yorke, now 49, has had next to no involvement with Harvey during his life and now, with Katie fearful that her son could die due to his weight, she has hit out at Yorke for not reaching out.
"He's a disgusting human for not wanting to know his son," she told The Sun.
"I play the mum and dad role to him, so I am protective. He is a unique child and he's very special."
Katie also opened up about the extent of Harvey's dangerously strong appetite, revealing that he has been known to steal pizzas from the freezer and eat them raw.
"I tell him he'll die and he says, 'No, don't be silly, Mummy's only joking'," she said. "He doesn't understand. He's always been a big boy, always been chubby, but now it's ridiculous.
"His clothes are 7XL, there are only two shops on the internet where I can get clothes for him.
"He walks up the stairs and he's sweating and out of breath.
"I'm really upset and worried about Harvey's weight because now it's on, the damage is done."
Yorke has previously blamed his busy schedule and having been based in Manchester for his limited contact with Harvey.