When Madonna accused Gwen Stefani of copying her style last week - "She ripped me off. She married a Brit, she's got blonde hair and she likes fashion" - it seemed like business as usual.

She was voted best international female artist at the 2005 Brit Awards and the album, which marries 1980s mutant electro-pop with hip-hop, has sold a staggering five million copies.

More remarkable still in the racially segregated world of American radio and MTV, Stefani, a white singer-songwriter, has achieved crossover to a black audience.

The album's most polemical track, "Long Way To Go", deals with race issues and ends with a quote from Martin Luther King's "I have a dream" speech.

Known for her outrageous fashion sense (who else would dare to wear a fur stole and hotpants, accessorised with crown and sceptre, on her album sleeve?) she also runs her own diffusion label, L.A.M.B. The range already has a cult following which includes Cameron Diaz and Paris Hilton.

In September, Stefani staged her debut catwalk show in New York, and Anna Wintour, the steel-tongued editor of US Vogue, declared, "We will soon see Gwen Stefani's range L.A.M.B.

competing with Donna Karan's DKNY."With her ash-blonde bleach and slash of carmine lipstick, Stefani combines old-fashioned Hollywood glamour with tomboy cool.

After a cameo as Jean Harlow in Martin Scorsese's The Aviator, it's been announced that Stefani will play Richie Berlin in Factory Girl, alongside Sienna Miller as Edie Sedgwick, doomed muse of Andy Warhol.

A self-confessed "dork" and "geek", she admits she has to watch her weight and makes no secret of the fact that her biological clock is ticking, as the first single from her recent solo debut, "What You Waiting For?", chronicles.

According to Sarah Ivens, editor of OK! in the US, "Gwen is constantly daring to be different, and searching for all things radical and trend-setting, while remaining almost sugary sweet.

"Her songs aren't just about love - they are about friendship and fights and standing up for yourself - useful things for teenagers to learn about."

So is Stefani the sex goddess with the Minnie Mouse voice, or the earnest family girl who claims she has only ever had two boyfriends and who lived with her parents until she was 30?

"She seems very benign and wholesome," says Garbage singer Shirley Manson, who has known Stefani since the mid-Nineties, "but underneath lurks an incredible toughness and powerful directness."

A shy girl who spent most of her time in a bedroom plastered with Marilyn Monroe posters, she nevertheless assumed she was destined for greatness.

The band developed a cult following, but it wasn't until 1997 when they released the No 1 single "Don't Speak", inspired by the torturous end of Stefani's seven-year relationship with Kanal, that they achieved global status.

But in 1998 she met Gavin Rossdale, frontman of British band Bush, and four years later they married at St Paul's Church in Covent Garden, where Stefani wore a Galliano couture gown and the groom was escorted down the aisle by Winston, a sheepdog decked out in a rose-covered collar and lead.

Earlier this year a DNA test revealed that Rossdale is the biological father of Daisy, the teenage daughter of Pearl Lowe (from a brief fling 16 years ago).

But the marriage survived and earlier this year she quipped: "In my next life I am going to be a guy and I'm going to be a complete slut."After 18 years as a performer, she controls every aspect of her career, from videos to merchandising.

When Mrs Ritchie, pop's other big Italian-Catholic female, releases her new album, also inspired by the 1970s and 1980s dancefloor, later this month, it promises to be a fascinating battle of the bottle blondes.

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