The 23-year-old has left the couple's Los Angeles home and has no intention of returning, reports TMZ.
A rep for Montag said: "Heidi is looking to move out due to all the fake bad press that Spencer controls. She's tired of it and is looking for a place and wants to focus on her acting career."
The strain between the pair has reportedly been building for months, and a source insisted that the split "wasn't a sudden thing".
"I am not Heidi Pratt, I am Heidi Montag," the Hills star tweeted on Tuesday.
Montag recently denied that Pratt was controlling her.
