WHITNEY HOUSTON is blowing over $300,000 a year on drugs, sources say – and friends fear she’s locked in a downward spiral that will soon end in death.

With the R&B diva’s drug habit raging out of control, her entourage recruited a drug dealer who sold her $6,000 worth of cocaine during a tour stop in Europe in June, an eyewitness to the deal told The ENQUIRER.

Although the 46-year-old singer claimed to be drug-free during her TV interview with Oprah Winfrey, she was actually high as a kite at the time, said a source.

And while she’s been through rehab at least twice, an in-depth ENQUIRER investigation has discovered Whitney has spent an average of $6,300 a week on drugs – or an astonishing $327,600 a year!

"Whitney is a dead woman walking! With the amount of drugs she’s buying, she won’t be able to live long. She’ll be dead in months," her friend Marlon David, a party promoter, told The ENQUIRER.

The Grammy-winning singer’s sobriety came into question almost as soon as she kicked off her "Nothing But Love" comeback tour in February in South Korea.

"A friend of mine… is a drug dealer who deals in cocaine. One of Whitney’s people called him and said, ‘Whitney wants to party,’" David told The ENQUIRER exclusively.

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