The Supremes weren't just one of the most successful singing groups in the Sixties but of all time: even today their sales of more than 20 million records are outstanding and in their own day they were second only to the Beatles for No1 hits. Songs such as Baby Love and Where Did Our Love Go? didn't just rush to the top of the hit parade; they became embedded in the Western psyche. The Supremes' huge commercial success made Tamla Motown one of America's major record companies in the Sixties and introduced to the world a new and different face of black American musical culture from the blues and jazz of earlier eras.

It was a time of political anarchy in the Southern states of America as activists such as Stokely Carmichael and charismatic black leaders such as Martin Luther King stood up against the culture of segregation and discrimination that were seen by the rest of the world as a shocking indictment of the world's most powerful democracy. Although largely apolitical, the three young singers of the Supremes, Diana Ross, Mary Wilson and Florence Ballard, played a very definite political part, in that, for their fans, they provided a placebo by largely ignoring what was happening to their less fortunate contemporaries.

At the V&A, the fashion and politics of the Supremes era are bought together in a new show, The Story of the Supremes from the Mary Wilson Collection. There are about 30 of the group's outfits on display: figure-hugging and sparkly; the most stunning are three lime-green full-length mackintoshes made of satin. The dresses are glamorous without being too revealing.

After criticism of last year's Kylie show, the V&A has opted not for a simple game of dress-up but something much more rigorous. If Kylie was a celebration of one personality, this is much more about a period of American and world history, when up popped these three extraordinary, manufactured singers. They were, to some extent, “white” performers: they sang in a white way, they dressed in a white way. If people were frightened of Carmichael, how could they be frightened by these three bunny girls?

Reassuringly old-fashioned in their approach, the Supremes' songs were about all the things popular songs have always been about - the sadness of love and the betrayal of hope; disappointments and rejection - all sung in the sweetest of tones with a simple, repetitive background to help it all along. With more in common with the traditional close harmonies of a barber-shop quartet than the raunchy jazz of New Orleans, the Supremes were packaged and presented to be about glamour and gloss in a Madison Avenue dream of slick perfection.

Some of the frocks were designed by the legendary Hollywood designer Bob Mackie, but most appear to have been created by anonymous costume designers with the needs of studio lighting and cameras uppermost. In fact, the group could be said to have been made by and for television. Their impact across America was largely the result of no fewer than 17 appearances on The Ed Sullivan Show, where, revealingly, they wore costumes chosen by Sullivan and his production team.

With ratings in mind, the glamourous look decided on was sugary and almost totally sexless, the precise qualities exuded by high fashion models in the glossies. No matter what the lyrics were saying, the overall visual effect of the Supremes was chaste, girl-next-door wholesome, although it was clear that in the case of Diana Ross there was a smouldering sexuality just below the surface.

Although all three Supremes came from black working-class stock, their success, so carefully judged by Sullivan and the bosses at Motown, was based on presenting a middle-class form of black identity similar to that which Nat King Cole had evolved to further his career. Berry Gordy, the founder and boss of Tamla Motown records, knew that white acceptance was what made black performers into stars. Musically the Supremes' repertoire and presentation was cookie-cutter stuff, a complete negation of what black music had stood for over the previous 40 years. Instead of passion, there was charm; instead of belief in black identity, there was a sell out to the white man's commercial values. Instead of soul, there was a growing bank balance.

And yet, the Supremes' sound soon became accepted as a black sound, to be copied by white singers such as Dusty Springfield and held to be as authentically black as that of performers who stayed much closer to their cultural roots. Still, in their time, they were icons of black popular music and they have retained that iconic stature even though they broke up 38 years ago.

Until they changed their name and their focus - when Diana Ross began to be billed as the star of the group - their act was so perfectly honed to selling huge numbers of records that it barely needed to change. The high-camp elements were all there, almost from the very beginning - the extravagantly bouffant wigs, the hip-clinging cut of the sequined dresses and the dramatic eye make-up were all standard elements of the act. Their acceptability got them gigs in largely whites-only venues, including night clubs such as the Talk of the Town in London, and Copacabana Club and the Philharmonic Hall in New York.

The V&A's Supremes show feels like an aperitif to, one would hope, a much bigger exhibition covering the whole field of American musical culture in the 20th century and its continuing influence today. American black culture was based on its music and it was trailblazing. It gave voice to the underdog and encouraged minorities to stand proud and tall. Without the lynchings and segregation; without the Black Panthers and Carmichael; without the quiet dignity of Rosa Parks, would other minority movements have achieved what they have in the past 40 years? An exhibition examining the creative and cultural effects of the struggles, music, writing and art of black Americans is overdue in this country. It could even include the frocks.

The Story of the Supremes from the Mary Wilson Collection, at the V&A (020-7942 2966), until Oct 19

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