Maria Grachvogel, who was preparing her catwalk show at Claridge's, made a request for size 10 models, but she was told by agencies that only size 8 or smaller models could be provided.
In the five years since Grachvogel last staged a catwalk show, the accepted standard model size was an 8-10 and now it has shrunk to a 6-8.
"There is no doubt that in the past few years the girls at the top end have become thinner. You'd have to be a fool not to notice it," Guardian.co.uk quoted Sarah Doukas, founder of Storm model agency, as saying.
"It was tricky finding models in a size 10," Grachvogel said.
"Most of the girls we saw were at least a size smaller than that. I make all my samples in a size 10, and it's nice to be able to show them on a body that fills them out.
"I have always been someone who would request that model agencies send me their curviest girls. But this time even they were too tiny to fill a pair of size 10 trousers and make them look great," she added.
Grachvogel's experience adds a designer name to those of supermodels Kate Moss and Karen Elson as part of a growing number of voices from within the industry speaking out against size zero culture.
Commenting on her "waif" years to Interview magazine in August, Moss said she "never liked being that skinny".