Power dressing: the politics of the Oscars dress

In 1951, actress Marlene Dietrich stole the show at the Oscars in a slim-fitting black satin cocktail dress by Christian Dior. She didn't even win one of the coveted statuettes.

She had an understanding with the designer, who dressed her both on and off screen; in fact, he was written into her contract. "No Dior, no Dietrich," she told the producer of Hitchcock's Stage Fright in 1950. She ignored the legendary director's dictat that he have the final word on all his characters' wardrobes. "Dior was fashion," she said. "Dior was good taste. I went to Dior when he first started. There hasn't been any fashion since."

His attention to detail was exacting: Dior made Dietrich extract information from her contacts as to what everyone else would be wearing, and then set about making her gown in absolute antithesis. What colour was the décor? What was the set like? The lighting? Dior waited to hear from which side Dietrich would enter the stage, all the better to calibrate the slit in her skirt to show off her legs to their very best advantage.

Four years later, Audrey Hepburn mounted the stage – having first lost her way and ended up an upper box – wearing a bespoke Hubert de Givenchy dress made from white organdy. She had cemented a relationship with the designer and insisted on wearing his pieces in her films, much to the annoyance of Paramount's award-winning costumier Edith Head.

Affiliations like Dietrich's and Hepburn's marked an official beginning to the very special marriage of the fashion industry to the world of celebrity. Until then, actresses had relied on the omnipotent studios for their red carpet ensembles, for better or for worse. At the third Academy Awards in 1930, winner Norma Shearer modelled the same gold lamé gown designed by Gilbert Adrian, MGM's wardrobe supervisor, that she had worn in her film The Divorcée. In 1935, It Happened One Night's Claudette Colbert accepted the award in a skirt suit designed by Paramount's own Travis Banton. And Bette Davis' 1936 dowdy printed cotton ensemble, designed by Warner's costume designer-in-chief Orry-Kelly, caused outrage: not only did it contravene the event's black-tie dress code, but she had also worn it on-screen in the badly received Housewife, a role her studio had forced her to into and which she believed had lost her the Oscar at the previous year's ceremony.

Nowadays the bums on seats at the Kodak Theatre are clad in the likes of Armani and Valentino, Saint Laurent and Chanel – and Dior, of course.

Stylist Phillip Bloch, who dressed Halle Berry in Elie Saab to pick up Best Actress in 2002, recently estimated that stars appearing on Sunday's red carpet would have spent between £60,000 and £650,000. There's hair and make-up at up to £3,000; there's the stylist's fee at around £1,000 per day; an all-important tailoring service to ensure a gown fits as if it were created with no other body in mind can cost upwards of £900; shoes are between £400 and £800; and the dress, of course, can be anything from £3,000 to £20,000, depending on the label, and whether it is from an haute couture range or a more restrained ready-to-wear collection.

But generally dresses are loaned or gifted, rarely bought, and where once there was a "fit" between celebrities and their chosen designers, there is now an overarching need for patronage and exposure that means labels want to dress as many nominees as possible.

Stars may call on several design houses to create a gown for them; stylists like Bloch will present to them a rail of perhaps 50 or 100 for them to choose from. Securing a red carpet appearance is like winning a business pitch – there is an unspoken mandate for designers to include a full-length gown in their seasonal collections in order that someone starry might spot it. Labels fill their front rows with film stars and send them their finest finery in the hope of high visibility come award season.

Armani always does well in the red carpet headcount, worn by Cate Blanchett, Julia Roberts, Jodie Foster and Michelle Pfeiffer in the past, and has opened a strategic atelier in Los Angeles itself. Armani's West Coast representative Wanda McDaniel was the first "point person", tasked with persuading suitable stars to wear something from the latest collection. A younger batch of celebrities more used used to the frou-frou and taffeta of Oscar night praised Armani's simplicity and easiness to wear in the early Nineties.

Many other Italian labels are known for a high-octane glamour that sits well with the hyperbole of the Oscars. Versace has amped up the rock 'n' roll factor in the past for the likes of Courtney Love, while Susan Sarandon was honoured with Italian duo Dolce & Gabbana's first red carpet design, a full-skirted bronze halter-dress that she wore in 1996. Carey Mulligan appeared in a youthful Prada number last night, a label often thought to be rather esoteric for the red carpet, but whose interesting take on classic was a surprise hit of the event.

But the current vogue seems to be once again for French designers – with Zoe Saldana in directional Givenchy by Riccardo Tisci, Kate Winslet in Yves Saint Laurent and the all-American Sarah Jessica Parker in Chanel couture, Paris has the edge on cool, modern glamour. The lure of considered, less obvious Gallic elegance is as strong now as it was for Dietrich and Hepburn.