Revealing why she has now decided to speak out, Keisha said: "I think I didn't really recognise it as racism, because I didn't grow up in an environment where I had just all black friends.
"My friends were very mixed, I've got different races in my family and I also thought that being racist meant that you actually called someone a racist word."
Siobhan left the group in 2001 and was replaced by Heidi Range, while Mutya quit in 2005 with Amelle Berrabah brought in as a replacement.
Keisha says she was unfairly blamed for Siobhan's departure and things got worse when Mutya left.
She explained: "It all started when I was about 15, 16, it was when Siobhan first left. As young girls do, you have arguments, disagreements, fall-outs, as far as I was always aware, it was just like sisters falling out. And Siobhan and I are really good friends and still work together so even she recognises that we were just kids.
"But what started happening was journalists would write up the story and instantly take sides. They'd take Siobhan's side and it was like those two tough and rough girls from north west London and nobody asked us about it and what was our experience.
"I felt, especially after Mutya left, I took the brunt of that. But behind the scenes the girls were very supportive of me and told me to ignore everything that was being said because they know who I was.
"That was probably part of the reason why I felt I didn't need to speak out."
Keisha also claimed she was treated badly by her record label, revealing they branded her "difficult".
She said: "Signing the contracts, if there was something where I thought let me call me lawyer', it was always 'you're being difficult'.
"If it was songwriting, I wanted my share of what I'd written, it was 'this person will feel very bullied if you do that'. I was always under a lot of pressure."
And she credited her fans with helping her to see that she had been a victim of racism.
Keisha said: "It was the fans that pointed it out more so because it had started to feel a bit normal to me.
"Once George Floyd had passed away and this conversation had come up, I guess I felt safer to do it because everyone was coming up and it felt more unified.
"I've never had any bad racial experiences with the fans, they've always been very welcoming to me."
