Singer says it wasn't her decision to leave the group
Buchanan, who was the last remaining original member of the band before she left, wrote on Twitter.com/Keisha_buchanan, that a “lack of trust” contributed to her leaving.
She refrained from directly criticising former bandmates Heidi Range and Amelle Berrabah.
“Although it was not my choice to leave, it’s time to enter a new chapter in my life,” wrote the singer, who is set to embark on a solo career. “I have nothing but positive things to say about the girls and I wish them the best of luck.”
She added: “I would like to state that there were no arguments, bullying or anything of the sort that lead to this. Sometimes a break down in communication and lack of trust can result in many different things.
“Now I’m going to take some time to focus on me. I’ve been in this band for 11 years and I have achieved so much. This is not the end… but the beginning!”
Buchanan has been replaced in Sugababes by former UK Eurovision entrant Jade Ewen.