Schiffer, 40, also missed out on making an appearance at Paris Fashion Week because she had some last-minute work to do on her debut cashmere collection, which launched this week, also in Paris.
"Nobody believes me but I'm very shy," the Daily Mail quoted her as telling Vogue.
"I understood that I had to do it when I was modelling but now, since I don't have to do it, I'd rather not," she said.
She admitted to being "much better in small groups of people than on a stage with everybody looking at me", and she said that no amount of persuasion will change her mind.
"Designers are very clever at trying to persuade me to do it each season and it's flattering that they do, but nothing would change my mind," she added.
