Wyatt, who recently appeared as a judge on Sky1 show Got To Dance, has previously said that she is unsure about the future of the band and has revealed plans to create a new group without lead singer Nicole Scherzinger.
She has also admitted that she does not think of Scherzinger as a friend.
Wyatt has now revealed that she has decided to quit the band because of the "variables off-stage".
"I've left the group," she told Loaded. "I am so thankful for everything the Pussycat Dolls [have] brought into my life. But I have to say there were just too many variables that I couldn't agree with and I had to follow my heart. So I decided to kind of push on with my own life."
Wyatt added: "Money and fame can't buy happiness. Ultimately I think that happiness is the most important thing in life and I think that once I started to get to know myself more and more I was like, 'You know, I don't think that happiness is within this group right now'.
"I wish that it was different because I love what we do on stage. I love being a Doll, but as far as the variables off-stage are concerned - I just couldn't do it anymore."