Bill Clinton's White House was a seedy "brothel" where the "horndog" president entertained a veritable harem of mistresses, a former US Secret Service agent has claimed.

But aside from the affairs , Gary J Byrne, the author of new tell-all "Crisis of Confidence", said one of his biggest challenges in dealing with the "goddamn unprofessional" Mr and Mrs Clinton was protecting them from each other.

Mrs Clinton, the book alleges, was a gun-loving domestic abuser prone to violent fits of jealousy which could all-too-easily be brought on by her husband's insatiable appetite for sex .

Byrne claims Clinton was dallying with Eleanor Mondale, the daughter of Jimmy Carter's vice-president Walter Mondale, at the same time he was seeing a certain 22-year-old intern.

Never the twain shall meet...Byrne said ensuring Lewinsky (left) and Mondale never crossed paths was a nerve-racking task. (AAP/Getty)

"I stood guard, a pistol at my hip, outside the Oval Office, the last barrier before anyone saw Bill Clinton," Byrne writes.

"The last barrier before Monica Lewinsky saw Bill Clinton. Yes, I’m that Secret Service officer."

One one occasion, Byrne says, a colleague of his was forced to be blunt with Lewinsky when she demanded to see the president, despite it becoming rather apparent that he was "screwing with Eleanor in the Oval Office".

"You have to wait," the agent told Lewinsky. "He’s with his other piece of ass. Wait till he’s finished."

Byrne claimed he did everything he could to keep Lewinsky away from Mondale and one of Clinton's secretaries.

He said he juggled this while keeping all of them out of sight of the "tyrannical" Hillary, but the president did not make it easy.

"Does that look like semen to you?" a steward asked Byrne one day, holding up a towel embroidered with the White House standard.

"Yeah, that sure looks like it," Byrne replied. "What the f--k and who would...?

Don't tell Hillary...The First Lady and now Democratic presidential nominee was a formidable presence around the White House. "Good morning, First Lady," Byrne recalls an officer saying one day. "Go f--k yourself," came the reply. (AAP)

"Nel explained that he’d been finding — and cleaning — semen- and lipstick-stained towels for weeks. I was shocked. If the stains didn’t rinse out, he’d carefully remove them by hand. He was terrified that if he passed them on to other Navy laundry personnel downstairs he’d not only reveal Bill Clinton’s affairs, he’d embarrass the presidency itself," Byrne writes.

Embarrassment was one thing, but Byrne also claims that Hillary, though probably aware of Bill's infidelities, was so unstable that his nerves were shot trying to keep her out of the loop.

He claims he once saw Mrs Clinton, her face set in a sardonic smile, unloading a Tommy gun into a firing range target's crotch after her husband's 1998 impeachment.

"What if she ran into the president with Monica or with another mistress?" Byrne wondered.

"Would I have to protect the president from his irate wife — or even from a mistress?"

The timing of the release of "Crisis of Character: A White House Secret Service Officer Discloses His Firsthand Experience with Hillary, Bill, and How They Operate" has already begun sending shockwaves through Hillary's presidential campaign .

As damning as Byrne's comments on Mrs Clinton may be – "a faux leader (whose) 'brand' was her only concern" – it might be his appraisal of the pair's ability to operate at the highest level that hits hardest.

"These people were, frankly, so goddamn unprofessional," Byrne writes, though he saves his most scathing appraisal for the former president.