Following weeks of reports the couple were to separate, the British TV star has released a no-holds barred statement confirming the end of her relationship with the cage fighter.
Katie blames the break-up on Alex becoming "fascinated by life in the media eye" and insists the pair tied the knot "too quickly" after dating for just seven months.
In the statement, she said: "Alex and I have had a number of difficulties over the past few months. I accept that these were in part caused by my marrying too quickly - we all make mistakes and this was one. However, Alex changed from the man I fell in love with and some of his behaviour became difficult for me to understand and caused issues. I have tried to help him with these issues but they have put a considerable strain on our relationship.
"Our difficulties were also not helped by Alex becoming more fascinated by life in the media eye. Obviously I cannot be critical of someone wanting to do this and originally I tried to help him with his career by getting him contracts with my production company. If Alex wants to honour those contracts the production company is more than happy to do so. However, Alex`s desire to promote himself caused a change in the dynamic of our relationship and contributed to our alienation."
The 32-year-old beauty also revealed she is furious with Alex, 35, for posing for photographs with her five-year-old son Junior - whose father is her ex-husband Peter Andre - in a martial arts gym and says she feels "let down" by his actions because he knows she wants to keep her kids out of the public eye.
Katie - who also has a three-year-old daughter Princess Tiaamii with Peter and an eight-year-old son Harvey from an earlier relationship - added in the statement: "I had hoped that Alex and I could remain friends but I am not sure if that is possible given events since last Sunday (16.01.11) when we were on the verge of releasing a statement. Alex asked that we did not release any statement because he wanted more time to think. The intervening period has, however, seen a number of false stories appear and photographs of Alex with my son Junior in the gym which it is absolutely clear were posed for. Alex is fully aware that I have sought to remove my children from the public eye now they are of an age to understand and be affected by media coverage of them. I feel incredibly let down that he did this while asking me for more time to discuss our relationship."
Katie - who wed Alex in a private ceremony in Las Vegas in February 2010 - insists she is now determined to focus on her children but is disappointed the marriage failed.
She said: "I am deeply upset that my relationship with Alex has failed but I know it is the right thing for my children and I that we separate. My children are my absolute priority in this and they are being shielded from what is happening."
Alex has now moved out of the mansion he shared with Katie in Surrey, Southern England, and is believed to be moving back into his parents Carol and Bob`s house in Aldershot, Hampshire.