A blast from the past is threatening Britney Spears’ sobriety as former pal Sam Lutfi shops an “explosive tell-all” about the star’s spiral into despair.

Sam is ready to drop bombshells about sex and drugs-and offer a unique intimate peek inside the 26-year-old singer’s shocking meltdown earlier this year, according to a Star Magazine insider.

Amongst the explosive claims Sam could plaster in print is a time the pseudo-bodyguard “dragged Britney out of a cocaine party.”

Sam, who law enforcement officials and members of the Spears family have accused of once controlling every aspect of the pop star’s life, says “she was doing so many lines, she didn’t even know where she was.”

Sam denies he’s writing a book about the time he spent as Spears’ right-hand man, but tabloid insiders beg to differ.

“We hope he’s backing off, but money talks, and he could get a lot for a tell-all.”