Kelly Osbourne's dramatic 'weight loss' for Chicago role

She hasn't had plastic surgery either. And while corsets can be slimming, they're never that slimming.

What Miss Osbourne has had, in this publicity shot for her stage role as Mama Morton in Chicago, is a serious swipe of the airbrush.

Those who spotted the 22-year-old daughter of Sharon and Ozzy Osbourne in New York recently would find it hard to reconcile the pleasantly plump party girl with the svelte siren in the picture.

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New look: Kelly Osbourne has slimmed down dramatically for her Chicago role. Right: in June this year

"This is a really extreme case of retouching," said airbrushing expert James Facey.

"This looks like a combination of a very tightly fitting corset and an extensive amount of Photoshop computer trickery.

"You can tell from the thickness of her upper arms alone that everything has been shrunk.

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Back to black: Kelly showed off her transformation during an outing in London last week

"In cases like this, to make things easier for the artists, a body double is even used and the person's head placed on top.

"But if this is her body, then it has been stretched and thinned and there has been a large amount of retouching around the waist and arms.

"I would say the only part of this that is really Kelly is her bust area.

"She has never looked this good, ever. She looks to be a size eight in the PR shots. No basque can do that amount of work."

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Behind bars: Kelly is preparing for her West End debut

Miss Osbourne will join Chicago at the Cambridge Theatre in the West End on September 10 in her first professional theatrical role.

She follows a string of guest stars including Brooke Shields, Claire Sweeney and Denise Van Outen who have appeared in the show.

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Mama mia! Kelly will play Matron Mama Morton which was performed by Queen Latifah in the film version of Chicago

Miss Osbourne, who will appear in Chic ago for seven weeks, said: "It's been a dream of mine to be in the West End."

Her spokesman claimed only her "hair and chin" had been airbrushed in the publicity shots.