Carola Long: Stop mocking Madonna

Weekend Arts: The pop star begins her British tour tonight. It's fashionable to knock her but, says Carola Long, her music, her fashions and her style helped an entire generation of women to grow up

Irecently found myself eavesdropping on the conversation between the two fiftysomething couples sitting next to me in a restaurant. "Did you see those pictures of Madonna in the paper," said one of the men, clad in a droopy polo shirt. "She looks awful. She's too old to wear such sexy clothes." "She should dress her age," agreed one woman, dressed in no-sex-please-we're-married catalogue wear, and adopting the displeased expression of someone whose TV remote batteries had run flat just before Antiques Roadshow. They then went on to discuss different brands of pet food.

Not only did it seem inconceivable that this staid quartet were around the same age as Madonna, but also that they should deem their pedestrian personal style preferable to the singer's alabaster-skinned, almond-eyed, sexually charged bionic glory. They aren't the only ones. Madonna's 50th birthday has provided the occasion for a chorus of as much criticism as celebration, particularly by Camille Paglia and Germaine Greer.

But, for many women of my age (30) and older, Madonna has provided – and still provides –not only the soundtrack to our lives, but also a deliciously controversial image of female strength. And that is why we still have a keen sense of anticipation as she embarks on another UK tour.

I first cottoned on to Madonna's ability to shock aged about eight. My friend and I would sing "Like a Virgin", with the lyrics, "touched for the very first time," in the back of her father's car, and revel in the anxious irritation it caused him, while oblivious to the real meaning of the lyrics. Despite the opposition of the American right to Madonna's ability to corrupt young minds, our innocence remained intact. Back then it was the infectious beats that made it irresistible to sing along, but it was her dress sense that really captured my imagination then, as a teenager, at university, and now. Back in the Eighties she was the ultimate rebel, the too-cool-for-school girl whose ripped tights and bed hair were the seductive antithesis of the Sports Illustrated prom queens. It wasn't just that Madonna's look was attainable, but that it was a bit dirty, daring, and rough around the edges. Ten years later, the baby-doll grunge look with its fusion of classic screen siren platinum hair and tough, dominatrix boots, as perfected by Courtney Love, and attempted by my friends and me, owed a lot to Madonna. In the early 1990s she might not have been as edgy as other strong female musicians at the time such as Kim Deal, but like them she came across as being in charge of her own destiny and her own sexuality. Pornography might be assimilated into mainstream culture now, but when Madonna first masturbated with a crucifix on stage, then wore underwear as outerwear, it seem like an exhilarating transgression of establishment values.

Madonna is the most famous woman on the planet, and according to Martin Amis, she is also "perhaps the most postmodern personage on the planet". Madonna is like a collage of eclectic individuals, eras and symbols, that coalesce into an entirely new construct. In his 1992 newspaper article, Amis also highlights Madonna's "protean quality, her ability to redesign herself (evident in each new photo shoot: baby-doll, dominatrix, flower-child, vamp)" which "represents an emphasis of will over talent".

This is a widely held opinion about Madonna, that she makes up for a lack of ability and of natural beauty through sheer determination, tireless self-promotion and physical reinvention. Two years ago Germaine Greer wrote, "I am of the opinion, shared by many, that Madonna can neither dance nor sing." And when Madonna was still considered "the future of feminism", Paglia referred to her "nondescript plainness". Madonna isn't quite Maria Callas in terms of voice quality, but it has improved considerably. She's got a far superior voice than, say, Kylie, who is probably her closest rival in terms of female pop longevity. To say she isn't a good dancer is just ridiculous, as her recent revisitation of her dancer's roots demonstrate, and far from being plain, her strong, haughty nose, high cheekbones and finely bowed lips add up to a strikingly sensual beauty. Madonna's star quality is about energy, white-hot intensity, and a complete lack of self-consciousness.

In her early songs such as "Lucky Star" and "Borderline", the breezy superficiality of stylish, effervescent beats and hook-rich melodies are given depth by her personal charisma and confident, visceral, sometimes carnal vocals. Her early songs might have become the karaoke favourites, but it's her ability to evolve and experiment artistically that has fully exploited her talents and guaranteed her longevity.

She has veered from the fusion of Catholic soul-searching and gospel soul singing on "Like a Prayer", to the breathy, claustrophobic subversivess of the album Erotica, to the manic electronic psychedelia of Ray of Light. There have been some undeniable duds along the way, both musically and cinematically – Swept Away anyone? But how many other artists have had six hit albums since they released their first greatest hits?

Of course, image is almost as important as the music, when it comes to pop, and Madonna is a mistress of hers. Since the early Eighties she has been a constant source of inspiration to fashion designers, and fashion lovers alike, and the quality that has informed all her past looks is an exuberant love of experimentation for its own sake, rather than a bourgeois adherence to good taste. Her Desperately Seeking Susan period was one of her most influential, as young women everywhere copied her sulkily sultry mix of peroxided hair, fingerless lace gloves and layers of crucifix necklaces. That look look still influences designers today: at Givenchy this season designer Riccardo Tisci showed sheer blouses piled with crucifixes on chains, and he has cited Madonna as a source of inspiration. In a symbiosis typical of the singer, he is now designing some of the costumes for her forthcoming tour.

In some ways the underestimation of her talent seems like an attempt to position Madonna as an attainable, democratic pop star, someone we could all emulate if only we could be bothered to do four hours of yoga a day. In the golden age of Hollywood, screen stars were unattainable, but now people want to know that their stars are "just like one of us". They want them to be fallible and, generally, Madonna isn't. She's never had a public nervous breakdown; she's never been to rehab. Most celebrities set out to reassure us that they are normal. Madonna has attempted this through the odd gesture such as revealing her favourite brand of ale, but generally she makes minimal attempts to appear utterly normal, or to conform to people's expectations of how women should behave.

Now she is subverting one of the most widely held preconceptions of all: how a woman should be, look and behave when she reaches middle age. Most men find her terrifying because of her evident desire for control, and her hard, muscly physique. Many women, too, seem to find the fact that she still sings about sex – and dresses and poses provocatively – unsettling. Her refusal to slide into mild invisibility should be applauded. It might have looked as if she was about to go all Women's Institute when she published a children's book and conducted a public reading in a floral tea dress in 2003, but the one thing you can predict about Madonna is her unpredictability. More recently she was shimmying around in a high-cut leotard for Confessions on a Dancefloor, and has now reinvented herself as a dominatrix wrestler for Hard Candy.

"Don't stop me now, don't need to catch my breath, I can go on and on and on," Madonna sings on her new album track "Give It to Me". Here's to another 50 years.