It was 9am on a Tuesday and the 15 year old was due at school. But she'd just spent her fourth night doing cocaine and, after 72 hours without sleep, she was feeling suicidal.

"I was so paranoid I couldn't even leave the house. I bolted my bedroom door and lay there shaking with hunger and exhaustion, trying to figure out a way to kill myself because I couldn't face another day," says Louise.

"The only thing that made me feel better was chopping up another three lines of cocaine. A few minutes later, I was out of it on the bed."

Louise, now 18, became addicted to cocaine three years ago after being encouraged to take the class A drug by three older boys she met at a friend's party in her hometown of Birmingham.

"I took it and it made me feel happy,confident and chatty," she explains. "My grandmother had just died and I'd been feeling down, but the cocaine made me feel on top of the world."

She found herself craving more and by the age of 16, she was stealing from her family to fund her addiction.

"Mum used to shut herself in her bedroom for hours, sobbing and saying: ‘What can we do with her?' over and over again. I remember my dad crying and saying: ‘Please, please, pull yourself together.' But although I knew I was hurting them, I couldn't stop," says Louise.

"Before I started taking cocaine, I was an A-grade student and had been in the top classes for everything. My parents became worried sick when I started missing lessons. They confronted me and I admitted I was taking cocaine.

"My dad started going into work late so he could drop me off at the school gates, but I'd walk in one entrance and out the other one as soon as he left. He took me to drug counselling, but after a few weeks, I refused to go any more. And as soon as I was able to, I dropped out of school."

Use of cocaine has spiralled to epidemic proportions in the UK, with the number of British teenagers using it now the highest in the developed world. A new report reveals the number of 16 and 17 year olds being treated for cocaine addiction has soared by 67 per cent in two years. According to recent figures, more than 1,000 children are arrested every year after being caught with drugs in school.

Behind the statistics there are thousands of tragic stories of families shattered by cocaine – once an expensive drug but now available for as little as £25 a gram or £1.50 a line.

Earlier this year, talented 21-year-old Manchester University student Jake Knowles hanged himself after admitting to bouts of depression and suicidal thoughts brought on by regular cocaine use.

"Cocaine changed his personality," said his heartbroken mother Suzanne. "He took drugs to have the confidence to party. What happened to Jake is proof of what cocaine can do to people's minds."

Like Jake, Louise underwent a drastic change in personality within a year of taking cocaine. When she wasn't high, she was plagued by paranoia and depressive fantasies about killing herself, and her weight dropped from 10st to 6st.

"Mum and Dad tried to stop me leaving the house, but I'd just sneak out," she says.

The final straw came when her parents, a housewife and a car engineer, discovered she had plundered every penny from a bank account containing a £40,000 inheritance from her grandmother, using a building society card she had stolen from her mum.

"A year after I started using the account, my parents went in to withdraw money for a new boiler," she explains.

"When they discovered it was all gone they called the police, who told them their own card was being used. They found out it was me from CCTV footage. My dad began shouting and screaming at me. I grabbed a screwdriver and told him not to come any closer. He ordered me to leave the house – and when I came home later that night, the locks had been changed. I sobbed and sobbed. I had to move in with a friend after that."

Louise's friend was horrified at how low she had sunk and insisted on taking her to see her GP. There, the teenager realised she desperately needed help. She agreed to go for counselling and enrol on a recovery programme with the charity In-volve, and was treated at their Birmingham clinic.

She has since met a supportive partner who is helping her stay clean, and she's working hard to regain her parents' trust.

"Finding love has given me a future and helped me stay off drugs. My relationship with my brother and sister has improved, although they are still disappointed with what I did to the family. But I think it will take a long time before my parents forgive me," says Louise, who, a year on, still suffers from paranoia and depression.

Sarah Graham, a therapist running In-volve's anti-drug programmes, says: "Teenagers try cocaine while drunk and don't know what they're getting into. Addiction can happen very quickly."

Katie* started taking cocaine four years ago when she was 18 and working in a bar in Liverpool to fund her nursing training.

"A colleague offered me a line at the end of a shift," she says. "Three months later, I was spending £50-£100 a day, and I couldn't go to work without cocaine."

Katie, now 22, lost close friends through her drug use and became increasingly depressed, sometimes bordering on suicidal.

"The come-downs lasted for days so I took coke again to avoid them," she says."In six months I'd lost more than a stone and was a paranoid wreck. My weight eventually plummeted from 9st to 7st. I looked like a skeleton, but I just couldn't stop using."

The turning point came when Katie fell in love with an IT consultant and gym fanatic, who was vehemently anti-drugs. He convinced her to move in with him in Surrey, but said she had to give up drugs if she wanted to keep him.

"I moved away from all the old temptations, and I didn't know where to get cocaine. Slowly I got through the withdrawal stage and gave it up for good," she says.

The couple married in June and Katie now works as a nurse. She says: "I could have died because of cocaine. People need to know how quickly it can destroy your life."

For information about cocaine abuse go to Talktofrank.com. For advice on addiction visit In-volve.org.uk.

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PHOTOGRAPHY: SYRIOL JONES, ALAMY HAIR & MAKE-UP: CAROLE MAYE AT NEMESIS * NAME HAS BEEN CHANGED