Hillary Clinton’s failed US presidential election campaign against Donald Trump has been painted as dysfunctional, doomed by “infighting” among campaign staff and a flawed strategy.

Shattered, a book documenting the inner workings of the Clinton 2016 campaign team, also describes Mrs Clinton’s campaign manager Robby Mook as a “professional political assassin”.

Co-authors Jonathan Allen and Amie Parnes, who are both political journalists, interviewed more than 100 sources who have revealed behind-the-scenes details about Mrs Clinton and the actions of those around her during the campaign and shortly after the election verdict.

As Mr Trump took the lead in the polls among Republican presidential candidates, Mrs Clinton ignored crucial warnings from an unnamed long-time Clinton adviser, the book claims.

The memo read: “Fact, Donald Trump can defeat Hillary Clinton and become the 45th president of the United States.”

It warned her not to “underestimate his [Trump’s] capacity to draw people to the polls who normally do not vote”, which could “tip the scales in key states”.

The adviser suggested that the Clinton team should routinely add “three or four points to whatever [polls] say about his support” to account for this unknown factor.

But Mrs Clinton refused to take the caution seriously, failing to act on the advice.

Former senator Hillary Clinton and former president Bill Clinton at Donald Trump’s inauguration in January.

Around the same time, Mrs Clinton allegedly told an adviser: “I don’t understand what’s happening with this country.”

She admitted to an aide that her personality “engenders bad reactions from people”.

Mr Mook, who was widely portrayed in media reports as a modern-age data whiz, was exposed as having an “obsession with control”.

His “desire to maintain the kingdom rather than win the war” placed importance on the advancement of his career ahead of the success of the campaign.

Sources cited him as being willing to cut down a close ally to “save his own skin”.

Meanwhile Joel Benenson, a senior strategist for Mrs Clinton’s campaign, was hired with a $1 million win bonus.

The book claims he was “condescending, dismissive [and] nasty” towards his colleagues, including both Mrs Clinton and her husband and former US president Bill Clinton.

It reveals how he was quietly sidelined just months before the election.

In other new revelations, Mrs Clinton requested access to the campaign’s server shortly after her 2008 defeat to spy on her senior campaign staff’s email exchanges to see “who was talking to who [and] who was leaking to who”.

Her snooping unveiled internal conflict that appears to have been reflected in her most recent campaign effort eight years later.

The 45th President of the United States delivered a fist-pumping, rhetoric-filled inauguration speech.

Shattered alleges that former president Barack Obama criticised Mrs Clinton’s use of a private email server – which later prompted an FBI investigation – saying he believed it “amounted to political malpractice”, despite refusing to publicly condemn her actions during the campaign.

When news of the private email server broke and Mrs Clinton prepared her public response, she had apparently considered “joking” about it.

But it was not Mrs Clinton who had the last laugh.

When it became clear that she had lost, albeit after somewhat of a delay, Mrs Clinton asked an aide for the phone and dialled the number of her opposition.

“Congratulations, Donald,” she said.

“I’ll be supportive of the country’s success and that means your success as a president.”

But moments later she made a second phone call.

This time, to Mr Obama. An apology to the Democratic Party.

“Mr President, I’m sorry.”