The America's Got Talent judge accuses her ex of years of emotional and physical abuse, driving her to the brink.
"I know what it's like to be beaten down. I know what it's like to be punched, humiliated, isolated and to feel there is no way out except suicide," she writes.
In her message at the front of the book Mel insists "lies and mistruths" kept her trapped for long enough and now, "I want the truth to set me free."
She adds: "I am ready to say what really happened to me..." But in Brutally Honest, while she regularly alludes to violence, Mel includes no details of any of the several beatings she alleged she received from Belafonte in court papers during their bitter divorce last year.
DailyMailTV has checked with lawyers for Belafonte and the couple does not have a non-disclosure agreement - meaning there's nothing to stop Mel from telling all.
Belafonte, 43, has always denied domestic abuse and says he's never beaten her and to date no evidence has been presented to suggest otherwise.
Most shocking about Mel's explosive memoir - being published on November 27 - is the star's revelation about wanting to take her own life - an event she blames on her ex.
"I can't pretend I'm not living in some twisted, violent hell. My life is a mess and I want out," Mel writes.
"I was at rock bottom…I was exhausted, worn down by seven years of constant emotional abuse, mind games, degradation, threats and sexual exploitation. I was drinking too much – wine, vodka, tequila – and had lost all self-respect. I was lost."
It was December 11, 2014 and Mel describes the moment she tried to take her own life in heartbreaking detail. She also recounts how it was her second time trying to take her own life, the first being when she was aged 14.
She says her then husband Belafonte was less than sympathetic and tried to stop her from going to hospital - a claim he vehemently denies.
Mel also talks about taking cocaine a few weeks into filming X-Factor in 2014 and her addiction worsened from there. Her routine involved snorting two lines of the drug in the morning, taking five or six lines a day to find the "magic formula".
"The cocaine only made my depression worse and I was permanently anxious and on edge," she said. Mel insisted she never took the drug while shooting the X-Factor, but refers to cocaine as "something strong" to help her cope.
"I'm not proud of taking cocaine but I can't say it didn't help me to have a line of that white powder when I got up in the morning," she explained.
When she got home after a long day on set the craving came back. "The cocaine would come back out of my bag and up into my nose. One line, another line and yes, another and another," she said.
And in another apparent contradiction to what she had claimed in court papers Mel admits she is open to sexual experimentation, including threesomes.
The former Spice Girl claimed that during her marriage, she was coerced into trysts that Belafonte secretly recorded and later allegedly used as ammunition against her, threatening to release as sex tapes 'if she tried to resist the threesomes'.
But in her book Mel admits it was her idea to try a threesome and drafted in a female friend to take part.
She also admits she got a 'kick' out of her hubby filming their sex sessions.
"The threesome was my idea but of course my then husband was well up for it...I don't think it's shameful to experiment - as long as it is all consensual - and I believe women can enjoy and initiate sex just as much (if not a whole lot more) than men.
"I made a call and a friend of mine came over. We had a lot of champagne and a lot of fun. I fell asleep happy because we'd fulfilled a fantasy."
From there she says she 'enjoyed' threesomes and often initiated them herself, targeting LA party girls or lap-dancers, trawling nightclubs to pick out girls they found attractive. They also tried to drag celebrities into their 'sex web'.
Some girls like socialite Lady Victoria Hervey - said 'yes', some girls - like popstar Rita Ora - said 'no'.
Again this whole passage flies in the face of her claims in court papers that she was coerced into having threesomes.
Mel, who has had lesbian relationships in the past, admits that she finds women's bodies much more beautiful than men's bodies.
And she says she's tried her best to keep her own celebrity body in prime condition. Since her divorce she has had a series of cosmetic surgeries, she writes.
Mel claims she contacted Dr Chia Chi Kao, an experienced aesthetic and reconstructive surgeon in Santa Monica.
On the surgeon's website it boasts Vogue magazine said Dr Kao 'is single-handedly revolutionizing the future of facelifts.'
Mel wrote that in the space of a matter of months Dr Kao arranged for her to have a whole series of small surgeries on her 'face, eyes, boobs and stomach'. She didn't stop there.
Mel then contacted Beverly Hills cosmetic surgeon Dr David Matlock who specializes in laser vaginal rejuvenation.
"I wanted to have surgery straight away,' Mel explains. 'He told me I didn't need it and that for a woman with three children, I was in exceptionally good shape. But I knew I wanted this done."
Mel's book examines the highs and lows of her personal life and the death of her father, Martin Brown, on March 4, 2017 really hit home. She recalls driving up to Leeds to see him as his health deteriorated, his body consumed by cancer - but it didn't go well.
Martin had not spoken to his daughter for five years after she filmed a documentary in Leeds and didn't go to see him.
"My dad started shouting at me. 'Melanie. Mind your own business. Go back home. I don't want you here. He kept ranting saying that I'd forgotten who I was and that he never wanted to see me again."
She added: "I cried all the way back to London." Mel was devastated when Martin finally past away.
"I miss him so much it hurts. Sometimes I wake up in the night and I am crying. Because he's gone. Because so many years went by without us speaking. Because there are so many things I want to say to him. My dad. The first man I loved and the first man who broke my heart."
Interestingly, in the book Mel talks warmly about her close friend Rusty Updegraff and how a fall out with her husband meant they had to part ways ten years ago. But she says he soon came back in to her life after she divorced her ex.
She gushed: "I'm glad to say, Rusty is now sitting beside me now in my all white apartment close to the Farmers Market in downtown LA. We are laughing together and talking about old times. I never lost my friend. He waited for me to come back to him."
Presumably this narrative, seen in an early draft of the book, might change significantly in the final version to be published next month.
In September Rusty, who helped care for Mel's children, told DailyMailTV she was the 'world's worst mom'.
The restaurateur, 60, said his former friend drinks day and night, is addicted to sex and needs urgent help to get her on the straight and narrow.
Siding with Belafonte in his custody battle for daughter Madison, seven, he also said he feared for their children's welfare while living with Mel and someone needed to intervene.
His bombshell deposition filed in LA Superior Court on August 31 led to a judge ruling Mel had a drink and drug addiction – and ordering her to undergo four months of regular medical tests.
Belafonte also has temporary custody of Madison until the matter is resolved. Rusty added that Mel blaming her booze and drug problem on PTSD from an abusive marriage is complete nonsense.
"I met Mel years ago, in 2002, so saying that this is all caused by PTSD is crazy because she was this way before she met Stephen and I was there when she met Stephen," he said.
"She was partying hard back then, but today it has just escalated."
Brutally Honest is set to be published on November 27.
Where to get help:
• Lifeline: 0800 543 354 (available 24/7)
• Suicide Crisis Helpline: 0508 828 865 (0508 TAUTOKO) (available 24/7)
• Youth services: (06) 3555 906
• Youthline: 0800 376 633
• Kidsline: 0800 543 754 (available 24/7)
• Whatsup: 0800 942 8787 (1pm to 11pm)
• The Word
• Depression helpline: 0800 111 757 (available 24/7)
• Rainbow Youth: (09) 376 4155
• CASPER Suicide Prevention
If it is an emergency and you feel like you or someone else is at risk, call 111.
