"We didn’t really get a chance to gel," she explained in an interview with V magazine.
"I feel like we were thrown to the wolves in a sense," added Siobhan. "Major sort of divide and conquer tactics going on.
The Sugababes, whose hit singles included Freak Like Me and Round, Round, became known for their changes of line-up and reported catfights.
Siobhan Donaghy quit the group in 2001 and was replaced by singer Heidi Range. Mutya Buena departed in 2005 and was replaced just 48 hours by Amelle Berrabah. Keisha Buchanan left the group in 2009.
"I’m sad to say that I am no longer a part of the Sugababes," said Keisha at the time. "Although it was not my choice to leave, it’s time to enter a new chapter in my life.
"I would like to state that there were no arguments, bullying of anything of the sort that lead to this," she added. "Sometimes a breakdown in communication and lack of trust can result in different things." The singer was replaced by former Eurovision Song Contest entrant Jade Ewen.
Keisha has revealed that she cannot talk about her split from the Sugababes for legal reasons.
"Legally, I’ve been told I can’t go into detail," she said. "I can speak for England and I’d enjoy telling the world exactly what happened but I can’t. I pretty much found out when everyone did."
In 2012, the original line-up signed a £1million record deal with Polydor Records.
Mutya insists that they were all enthusiastic about reuniting. "It wasn’t out of desperation that we got back together."
Flatline, the first single under the band name MKS is released on 1 September. The girls will play a sold-out show at La Scala, London, on 1 August.