"The last time I worked with him, I only worked with him because literally I got blackmailed by my label," Clarkson alleges in a radio interview with Australia's KIIS FM. "It was a really hard time for me. They were like, 'We will not put your album out if you don't do this.'"
"He's not a good person to me," she continues. "We've clashed."
Clarkson worked with Dr. Luke, whose real name is Lukasz Gottwald, on two of her biggest hits -- 2004's "Since U Been Gone," and most recently, on 2009's "My Life Would Suck Without You." Both the singles are off albums -- Breakaway and All I Wanted -- released on RCA, which is owned by Sony Music Entertainment.
"Obviously he's a talented dude, but he's just lied a lot," she claims of the 42-year-old hit-maker. "I've come up on a lot of bad situations. Musically it's been really hard for me, because he will just lie to people and it makes the artist look bad. He's kind of difficult to work with, kind of demeaning."
Still, the "Piece by Piece" singer makes it clear that Kesha's allegations -- that Dr. Luke drugged and raped her over a decade ago and consistently abused her both physically and emotionally, which he has categorically denied -- never happened to her.
"Her situation is very different from mine, apparently. He never did anything like that with me. I don't know that part," Clarkson says. "I can't really say anything other than that… I wasn’t there. I don’t know specifically what happened in their situation. Obviously, I wasn't in the room."
"But I can remark on his character," she adds. "Unfortunately, when you have that poor of character -- like, so many artists don’t like you and don’t like working with you -- that's not normal. I get along with everybody I work with, I love everyone I work with, and he’s just not a good guy for me."
Dr. Luke's team had no comment to ET about Clarkson's allegations. However, a source close to the producer tells ET that he and producer Max Martin were asked to work with Clarkson.
Clarkson made it clear she supported Kesha on Feb. 19, tweeting, "Trying 2 not say anything since I can't say anything nice about a person... so this is me not talking about Dr. Luke." The post linked to a tweet by the band Best Coast, which read, "This is some legal bulls**t. #FreeKesha."
Trying 2 not say anything since I can't say anything nice about a person... so this is me not talking about Dr. Luke https://t.co/lLhtUHbmgG
"Her team actually hit us back confirming that I was serious about it, which is really cool," Zedd said. "I'm obviously very serious about it, so maybe something will happen. Maybe there's something I can do. Maybe we can do some music. Nothing I can say right now, but it would be cool."