A message sent from Katie's Twitter account told fans that she is leaving Kieran. The tweet came just after Katie announced that she is pregnant with Kieran's child.
The message accuses Kieran of having an affair with Katie's friend, which is alleged to have been going on for seven months.
Kieran has not yet responded to Katie's claims. Katie's rep has told Reveal that she cannot comment.
"Sorry to say me and Kieran are divorcing him and my friend been having a full blown sexual affair for 7 months," the tweet read.
Fans were left stunned by Katie's brief announcement, with some querying whether her Twitter account had been hacked. "Surely this is a joke?" asked one, while another said: "This can't be true."
On Sunday, Katie and Kieran confirmed they are expecting their second child together. Katie is also mum to kids Junior, Princess and Harvey from previous relationships.
Katie is said to be six months pregnant and only recently found out after a trip to the doctors.
The couple married in January 2012 on a beach in the Bahamas and welcomed their first child, Jett, the following summer.
In October 2013, Katie had told Reveal: "[Kieran] is brilliant, that's why I'm saying to everyone that I don't have to worry about being with someone else again. He is here to stay. Third time lucky."
Just a couple of weeks ago Katie and Kieran seemed as blissful as always, with Katie tweeting pictures of them looking loved up while on holiday in Cape Verde.
And on 21 April, she shared a close up photo of the couple's wedding rings as they compared their holiday tans.
Katie and Kieran celebrated their first weding anniversary on 16 January by exchanging cute messages on Twitter.
" I love you so much, 1 year today, can't wait for later ;)," wrote Katie, while Kieran said: "Happy anniversary my beautiful gorgeous wife @MissKatiePrice 1 year today.
"Been the best year of my life. I love you with all my heart! "
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