The porcelain collectable was described as "handcrafted to an unprecedented level" in the brochure of its manufacturer, Bradford Exchange.
"The world's finest artisans have created an authentic likeness of the handsome Prince on his wedding day," the text accompanying a picture of the doll, which costs £149.95, said.
"Crafted of fine bisque porcelain and meticulously hand painted for exquisite realism, this lifelike portrait is 17 inches tall, and full pose-able."
But the Advertising Standards Authority (ASA) - which asked for its own sample of the doll - upheld a customer complaint that the text was misleading.
"We considered that the face of the doll differed from that advertised in being slimmer and painted in a more vibrant, and less realistic, way," the ASA ruling said.
"The hairline also appeared to be more bluntly defined, and the doll's hair was in some parts much longer than the close-cropped style shown in the ad.
"Because we considered that there were significant differences between the doll and the image in the ad, and because we understood that the two were intended to match, we concluded that the ad was not an accurate representation of the product."
The advert must not appear again in its current form, ASA ruled.
Bradford Exchange, which trades as The Ashton-Drake Galleries, said it sold a large number of the dolls and received no other complaints.
It describes the limited edition piece as a "perfect accompaniment" to its Princess Catherine Royal Elegance Bride Doll.
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