The "Crazy" singer told "Access Hollywood" Friday that Joop is a veritable unknown attempting to make a name for himself by saying Klum was too busty and heavy to be a runway model.
"First of all, who is he? Is he a plumber or? I've never heard of him," Seal told "Hollywood" host Billy Bush. "I've never heard of him and to tell you the honest truth, I don't know if Heidi's ever heard of him before. It sounds to me like someone looking for a bit of publicity."
Joop is the founder of the JOOP! fashion company and previously served as a fashion editor for Neue Mode women's magazine.
"Access Hollywood" said Joop not only claimed Klum, 35, was no longer in the right shape to be a runway model, but said the former Victoria's Secret model "is not a top model, but an ad girl."
Klum immediately dismissed Joop's comments, saying she purposefully avoids being too thin.
"In this business you have to be fit, but I always try to be a good role model and not too thin," the model said.