London, July 16 : Marilyn Monroe's perfect hourglass figure made her a worldwide sensation but her famous curves were not all natural - they were enhanced by a 1950s version of a Wonderbra, which enhanced her cleavage, boosted her cup size and added more than an inch to her bust measurement.

And now, the bra that belonged to the Hollywood siren is going up for auction.

The brassiere was able to work its magic because it had under-wiring and four cups, an inner pair to hold her breasts and an outer pair an inch in front of the real ones to enhance her bust, reports The Times.

It is believed that the bra, or one very similar, was worn in The Seven Year Itch, when Monroe appeared in a white halterneck dress. The straps would have been concealed beneath the halter.

The cream and ivory-coloured bra was part of the wardrobe of Monroe's clothes sold in Hollywood in 2005. It is being auctioned in London on Saturday, when it is expected to fetch around 2,000 pounds.

Katie Halford, a designer for the vintage lingerie firm What Katie Did, said the style was known as a "fling" bra, and added: "They were a bit naughty. They were worn by strippers and burlesque artists in the 1940s and 1950s. Marilyn Monroe didn't like wearing underwear and, if she could get away with it, she wouldn't wear any.

"It would have given her breasts extra support and uplift and left her nipples exposed.

"It would have given the impression that she had very good and perfectly positioned breasts, while making it appear she wasn't wearing a bra at all, and because it is a bit padded, it would have made her breasts look a bit bigger." (ANI)