The glamour model announced earlier this week she and her boyfriend - who met at the Oscars in February last year - had "mutually" decided to end their relationship but would remain friends.
But Penna is reported to have told an Argentinian magazine: "I left her simply because she is crazy. Katie's brain is not wired right, or the wires don't connect properly.
According to Leandro Penna, he split with Katie Price because she was 'driving him insane'
"I don't know what's wrong with her. I was thinking it over recently and one day decided to pack my bags and leave.
"There was nothing else I could do. She was driving me insane," he told Caras magazine.
Despite an earlier brief split, Penna added there was no going back, reportedly saying: "Katie is totally crazy."
In a statement on her website this week, Price said the split was amicable: "We will always feel deep affection for each other, but sometimes relationships just run their course ... we've mutually decided to call it a day, but we really wish each other nothing but the very best and will remain best of friends."
She recently denied reports she sent flirty messages to X Factor contestant Dan Ferrari-Lane from the group District 3.