Donald Trump hopes to use a damning tell-all by an ex-Secret Service officer as ammo against Hillary Clinton, The Post has learned.

“The book appears to be a treasure trove of new information and we really look forward to mining it,” an insider working on the presumptive Republican nominee’s campaign said Monday.

The Post’s Page Six exclusively revealed details of Gary Byrne’s upcoming memoir, “Crisis of Character,” which is based on what he learned while stationed outside Bill Clinton’s Oval Office.

In the book, due out on June 28, Byrne writes that Hillary Clinton has a “Jekyll and Hyde” personality that terrified White House staffers while she was first lady and that now makes her unfit to be president.

Two veteran GOP operatives said voters shouldn’t ignore the red flags.

“When a Secret Service officer is openly warning the public about a presidential candidate’s temperament, it’s a bona fide problem,” said consultant Bill O’Reilly, who isn’t working for Trump.

Trump pal Roger Stone, who penned his own anti-Hillary book last year, also noted that Byrne was “ telling what he sees. It’s very compelling.”