Booker Prize winner Hilary Mantel has launched a damning attack on Kate Middleton, branding her "plastic" with "dead eyes".
Mantel made these comments during her lecture for the London Review of Books entitled Undressing Anne Boleyn.
In it, the 60-year-old Wolf Hall author compares the Duchess of Cambridge to Princess Diana and Marie Antoinette, saying she is just a vessel through which the Royal family can breed.
She said: "I saw Kate becoming a jointed doll on which certain rags are hung. In those days she was a shop-window mannequin, with no personality of her own, entirely defined by what she wore.
"These days she is a mother-to-be, and draped in another set of threadbare attributions. Once she gets over being sick, the press will find that she is radiant. They will find that this young woman's life until now was nothing, her only point and purpose being to give birth."
Mantel says both Marie Antoinette and Diana were similar, whereas Kate stands apart due to her excessive grooming: "Antoinette as a royal consort was a gliding, smiling disaster, much like Diana in another time and another country.
"But Kate Middleton, as she was, appeared to have been designed by a committee and built by craftsmen, with a perfect plastic smile and the spindles of her limbs hand-turned and gloss-varnished.
"When it was announced that Diana was to join the royal family, the Duke of Edinburgh is said to have given her his approval because she would 'breed in some height'. Presumably Kate was designed to breed in some manners. She looks like a nicely brought up young lady, with 'please' and 'thank you' part of her vocabulary."
Speaking about the Duchess' portrait by Paul Emsley, Mantel says: "Her eyes are dead and she wears the strained smile of a woman who really wants to tell the painter to bugger off.
"Kate seems to have been selected for her role of princess because she was irreproachable: as painfully thin as anyone could wish, without quirks, without oddities, without the risk of the emergence of character. She appears precision-made, machine-made, so different from Diana whose human awkwardness and emotional incontinence showed in her every gesture.
"Diana was capable of transforming herself from galumphing schoolgirl to ice queen, from wraith to Amazon. Kate seems capable of going from perfect bride to perfect mother, with no messy deviation."
Mantel has been widely criticised for her comments on Kate Middleton, with Telegraph women's editor Emma Barnett branding the attack "cheap and cruel".
Barnett wrote: "We will learn what the Duchess of Cambridge cares about through small signs - such as which charities she lends her support to, or what events she chooses to attend.
"But we will never learn more about her from a self-indulgent, albeit extremely well written, hour-long lecture for the London Review of Books (this is the literary award magnet Mantel we are talking about after all).
"And unlike all those 'regular female role models' (whether they consider themselves ones or not) out there, the Duchess of Cambridge can't fire off her real feelings about Mantel's foul comments on via her Twitter account this evening, or go on TV to express her views.
"As a fully paid-up member of the royal family, she can only respond by doing the very same thing Mantel has criticised her for: staying quiet."
Ingrid Seward, editor-in-chief of Majesty magazine, also said Mantel's comments were unfair.
"Kate's duties mean she can't do anything that might reveal (her) personality," she said.
"They have to be nice to everyone. They are probably stupefyingly bored but they can't appear to be having anything other than a nice time."
Royal commentator Richard Fitzwilliams told the Metro: "The Duchess has millions of admirers around the world and is a woman of great charm. Hilary Mantel's comments are ridiculous and say more about her than the Duchess."
St James' Palace has not commented on Mantel's attack, but last week said it was disappointed at Italian magazine Chi's decision to print pictures of the Duchess in a bikini on holiday in the Caribbean.