With her addictions behind her, Kelly Osbourne puts on her dancing shoes

Kelly Osbourne was once relying on painkillers just to see her through the day. Now she's clean, healthy and dancing on prime-time television.

It's a remarkable change for the former wild child of rock legend Ozzy Osbourne, 60, and his wife Sharon, 56. The star has battled with personal demons since she was thrust into the spotlight at the tender age of 16 - troubles that she details in her new autobiography, Fierce.

‘Vicodin was my confidence in a bottle,' writes Kelly, who has recently joined the cast of Strictly Come Dancing, the UK version of Dancing with the Stars. ‘I was waking up emptying six Vicodin into my hand. Soon I was taking 50 pills a day. Most people would overdose on 10.'

The 24-year-old admits the pills helped her ‘hide the terrible sadness' she felt after moving to the US, where she was constantly scrutinised after appearing on TV in The Osbournes, the fly-on-the-wall documentary about her family.

‘The fame was instant and I found it confusing,' writes Kelly, who concedes alcohol was also a problem, but the lesser of two evils.

‘There were magazine articles calling me fat,' she continues. ‘I wasn't skinny but as a UK size 10 I wasn't fat. I felt like someone was crushing my heart. I was practically a child, yet all of a sudden I was public property.'

The star, who divides her time between London and LA, reveals her addiction worsened when Sharon was diagnosed with colon cancer in 2002, and soon after her father had a near fatal motorcycle accident. Ozzy and Sharon first suspected Kelly's drug troubles after she fell asleep at the dinner table. But when pictures emerged in the papers of her buying drugs, Kelly was sent for her first of four stints in rehab in just six years - the latest of which was this January.

‘I do feel like I let a lot of people down - mostly myself, to be honest,' Kelly says of her addiction. ‘It's easier to label me as a celebrity daughter, trust-fund kid and party girl than to ask what I'm like. And I allowed that to happen. So all the good stuff I did didn't matter, because I'd go out and drink and f**k it up.'

Although her latest stint in rehab was a success, Kelly's aware that it wouldn't take much for her to return to her old habits.

‘I'm realistic,' she says. ‘For the first time, I've learnt my biggest lesson - there's a chance I'll relapse.'

Drug troubles aside, Kelly's keen to prove she's turned over a new leaf, and leapt at the chance to compete on Strictly Come Dancing. With it's vigorous five-hour daily training sessions, it's a move that's helped her both maintain a healthy lifestyle and tackle her weight issues, with which she's constantly struggled.

‘I've never felt so healthy,' says Kelly, who's lost more than six kilograms since she started on the show. ‘By the end of it I'll be a lean, mean machine. It's so amazing. I've tried so many stupid fad diets to try to lose weight, when all I needed to do was dance.'

Feeling sexy, confident and fit, Kelly's also blissfully happy with her fiance Luke Worrall, 19.

‘It's made me love him 10 million times more because he stuck by me,' says Kelly, who hopes to emulate her parent's relationship. ‘My parents are so in love it's scary. Their relationship gives me a lot to live up to. But I hope me and Luke will have the same thing.'

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