Hillary Clinton has a “Jekyll and Hyde” personality that left White House staffers scared stiff of her explosive — and even physical — outbursts, an ex-Secret Service officer claims in a scathing new tell-all.

Gary Byrne, who was posted outside the Oval Office when Bill Clinton was president, portrays Hillary as too “erratic, uncontrollable and occasionally violent” to become leader of the free world, according to advance promotional materials exclusively obtained by Page Six.

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The book claims she repeatedly screamed obscenities at her husband, Secret Service personnel and White House staffers — all of whom lived in terror of her next tirade.

Secret Service agents had discussions about the possibility that they would have to protect Bill from his wife’s physical attacks, Byrne writes, and the couple had one “violent encounter” the morning of a key presidential address to the nation.

Meanwhile, a paranoid Hillary Clinton tried to have the Secret Service banned from the White House and once tried to ditch her security detail, Byrne says.

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Byrne says he walked into a room where the president was “involved inappropriately with a woman” who was neither his wife nor Lewinsky.

And he says he once threw out a White House towel stained with a woman’s lipstick — and the president’s “bodily fluids.”

Byrne describes arriving for work one day in 1995 following a loud fight between the Clintons the night before.

The dust-up, he says, left a light blue vase “smashed to bits” and Bill sporting a “real, live, put-a-steak-on-it black eye.”

This book is similar to an earlier, similarly themed book by former FBI Agent Gary Aldrich called “Unlimited Access: An FBI Agent Inside the Clinton White House.” That book painted a the same picture of a harridan Hillary who brutalized staff and had the mouth of a fishmonger’s wife besetting an irresponsible, but likeable, horndog, Bill Clinton. Aldrich is the source of the story of Clinton sneaking out of the White House for late night trysts.

Where this book differs is that the Aldrich book appeared in 1998 and no one really cared. This one hits in a hotly contested election year and has much more of a chance of having an impact on the presidential campaign than any similar book in modern history. Hillary is already deeply unpopular with voters and is widely believed to be dishonest. Watching her for five minutes on television will convince even the most rabid Hillary fan than she is a vicious, embittered shrew who undoubtedly screams at staff and probably keeps a small dog to kick in those special spittle-flecked moments of divine rage.  To the extent this book confirms what any lucid person thinks about Hillary, it is going to hurt her with voters, it will give her and her surrogates anxious moments in interviews, it is going to make her attacks on Trump’s temperament less than effective and it will give Donald Trump’s twitter feed all the material it needs.