Dr. Luke allegedly blasted Kesha about her weight in 2012.
The star has submitted a number of emails between the music producer and her manager Monica Cornia as evidence, in her ongoing legal battle to end their professional relationship, that he was critical of her appearance.
In the documents, obtained by DailyMail.com, Dr. Luke allegedly wrote: "Nobody was calling anybody out. We were having a discussion on how she can be more disciplined with her diet. There have been many times we have all witnessed her breaking her diet plan. This particular time - it happened to be diet coke and turkey while on an all juice fast."
He reportedly added: "A list songwriters and producers are reluctant to give Kesha their songs because of her weight."
Kesha has accused Dr. Luke of sexually abusing her but he has denied the claims and it was recently reported that the 43-year-old record producer - whose real name is Lukasz Gottwald - wants to add a defamation charge to his own lawsuit against Kesha, after she allegedly sent a text message to fellow musician Lady Gaga, claiming there was another victim.
Dr. Luke's lawyer Christine Lepera told Page Six in a statement: "Dr. Luke seeks to add an additional defamation claim against Kesha based upon the discovery of another false and defamatory statement she made about him that was part of her calculated effort to harm his reputation and business.
"Kesha's new proposed counterclaim simply repeats the meritless and untrue allegations that were set forth in her earlier pleadings and which Dr. Luke fully disputes."