"It's Miss Middleton's intention to keep the dress a secret for her bridegroom on their wedding day, as is every bride's prerogative," the unnamed spokesman said of the dress to be seen by millions of people around the world April 29.
There was speculation designer Bruce Oldfield was a possible candidate after Middleton's mother and sister were seen in his upscale Knightsbridge store, People magazine reported.
Britain's News of the World said the shopping trip gave "a big hint he's been picked to design the royal wedding dress."
Oldfield, who was a favorite of the Prince William's late mother, Princess Diana, has kept mum about a possible wedding gown for Middleton, but said in December, "Kate has such a gorgeous figure that she would look stunning in anything."
Kim Kardashian, Kanye West reportedly set wedding date
Aaron Carter is still in love with Hilary Duff