Chantelle's decision to break up with the cage fighter has come just two days after he was arrested at their home in Essex on suspicion of "criminal damage and using violence to force entry".
The mum-of-one tweeted: "Unfortunately, I have had no option but to end my relationship with Alex."
Last night, Alex released a lengthly statement on his official website about his romance with Chantelle.
The star, who had a daughter with Chantelle just 11 weeks ago, apologised for his recent actions, saying he hoped to "earn" fans "respect and trust" again.
The statement read: "I have disappointed and hurt many of you, as indeed I have my family. For this I am truly and deeply ashamed of myself.
"Since my split from Kate, I have tried to forge an independent career for myself based upon the advices given to me by my management team.
"These advices and the choices that I have made as a result, I now accept have been wrong."
Alex went on to add: "The birth of my daughter Dolly was a profound turning point in my life.
"Everything that I had done previously suddenly seemed petty and small – this tiny little girl awoke something in me that I never knew existed.
"And since Chantelle gave me this precious gift, I really have tried to take stock of my life.
"I have decided that this situation can no longer persist and above anything else, I must try to become a good father and a loyal husband.
"I have a lot of learning to do and I know that I need to earn your trust and respect all over again."
Just two days ago, Alex was arrested and taken into police custody near his home in Brentwood.
Beforehand, neighbours reportedly heard a man shouting: "Let me in, f**king me in!" and officers were later seen at the couple's home.
Alex was released without charge, with no further action being taken, but he has refused to reveal why he was arrested, saying it was a "private matter".
Read more: Alex Reid refuses to say why he was arrest at his and Chantelle Houghton's home in Essex
Read more: Alex Reid released without charge following arrest at his home