Price, 35, who is six month pregnant with Hayler's second child after welcoming their first baby Jett Riviera last August, said she was shattered to learn about the affair.
"Sorry to say me and Kieran are divorcing. Him and my best friend Jane Pountney Bee, having a full blown affair for seven months," Price tweeted.
"Kieran is a disgusting human being doing this after I've just had a baby and still doing it till I caught them. No human being deserves this especially being six months pregnant. Worse pain in the world," she wrote further.
She has was previously to Australian pop star Peter Andre and Alex Reid. She has two children, Junior and Princess Tiaamii with Andre, and a son, Harvey, from a previous relationship.