The legendary fashion designer is a big fan of the party planner's older sister, Duchess Catherine, and thinks she makes a good wife for Prince William, but is less than enamoured by Pippa.
He said: ''Kate Middleton has a nice silhouette and she is the right girl for that boy. I like that kind of woman, I like romantic beauties.
''On the other hand, her sister struggles. I don't like the sister's face. She should only show her back.''
As well as being a fan of Catherine, Karl is also full of praise for Victoria Beckham - who has children Brooklyn, 13, Romeo, 10, Cruz, seven, and Harper, 12 months, with husband David Beckham - because of her slim figure.
He added to Grazia magazine: ''She is great. I like her a lot. I have known her for many years.
''She had a career as a singer. She has a beautiful husband and stunning children and now she makes a career in fashion.
''And that body, after four children. There are not so many who have a body like that. She is very disciplined.
''We have the same eating habits. We did a full fashion shoot with her styled as COCO CHANEL in less than three hours.''