The 25-year-old singer allegedly hinted that her old bandmates Heidi Range and Amelle Berrabah may struggle without her in an interview with the Daily Star.
Buchanan is quoted as saying: "I did a lot of stuff behind the scenes for the band that people don't know about. I was always the one working hard."
The popstar, who founded Sugababes with Mutya Buena and Siobhan Donaghy in 1998, was ousted from the girl group in September following rumoured bust-ups.
Discussing her future as a solo artist, she said: "I'm doing what's best for me. They did what's best for them. The fact is, I was in the Sugababes for 12 years. I was in that band because I loved it, not to elevate myself. But you have to move on and I've got Mutya and Siobhan supporting me now."
Buchanan recently spoke out to deny rumours that she is reforming the original Sugababes with Buena and Donaghy.