Whitney Houston paid $400,000 to save the life of then-hubby Bobby Brown after the bad boy singer was held for ransom by a murderous New York gang, according to a new book.

The author, ex-convict David Collins, was a member of the gang – known as The Preacher Crew. And in an exclusive interview, Collins told The ENQUIRER how poor Bobby wound up naked and hog-tied at a gang hideout.

"It was April 1993. Whitney’s movie The Bodyguard and the movie’s album were big hits," said Collins, whose book  Preacher of the Streets tells the inside story of the gang and Brown’s kidnapping.

According to Collins, Bobby got about $25,000 worth of cocaine from a dealer in New Jersey, where Bobby and Whitney lived – and told the dealer he’d pay him later. But soon the drug dealer was fuming because Bobby couldn’t be reached.

The dealer, Luke, was on a visit to Atlantic City when he bumped into a friend, Clarence Heatley, a 6-foot-7, 260-pound mountain of evil who was kingpin of the notorious Preacher Crew gang.

Heatley – whose fiery oratory earned him the nickname "Preacher" – dealt his poison in Harlem and the Bronx.

Torture was the gang’s trademark. Members would slice off body parts of rival dealers before killing them. When Preacher met Luke in Atlantic City, Luke mentioned that Bobby Brown owed him about $25,000 and was ducking him.

"Preacher came up with a plan to make himself a lot more than $25,000," said Collins.

"He paid Luke the money Bobby owed and told Luke, ‘His debt is now my problem.’"

For the full story behind Bobby’s kidnapping and Whitney’s heroic pay-off to the gang, pick up the latest ENQUIRER – on sale now!