The singer has been undergoing treatment in Britsh rehab clinic the Priory in recent months after being admitted with drug and alcohol problems earlier this year.
He has now revealed the extent of his drug addiction and decided to leave the group after staying clean for over two months.
Speaking in a U.K. tabloid today, Hawkins commented: "I hit absolute rock bottom. I spent over £150,000 on cocaine in three years--a frightening amount.
"I was consuming up to five grams a day which cost me £1,000 a week, sometimes more. I regularly used to stay up for four days at a time on coke and alcohol binges.
"I became secretive, volatile, and verbally abusive, a really unpleasant person to be around. There were lots of periods I don't even remember, blackouts," he told The Sun.
Speaking about his addiction to cocaine, he continued: "It affected every single decision I made. Everything was decided on the basis that I wanted to take cocaine at some point. I would demand that we were the first on at awards shows so that I could get on with my drinking and drugging.
"I feel like I've lost three years of my life. I'm only just coming to terms with what has happened because I was always off my face."
The Darkness will now apparently continue with a new frontman, while Hawkins plans to take more time out before beginning work on other projects, including a solo album.
He said: "I feel bad for the others. It will be an upheaval. But it's time for me to move on. It would be damaging to my recovery to stay on.
"I'm not blaming the band for my problem--I am an addict. There are people who can be in bands and stay clean, but I'm not one of them.
"I am going to do a solo record at some point and get into scoring films. But this is all new so the future is still uncertain."
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