The book had been “tentatively” scheduled for this autumn. Last year, Prince Harry said he was creating an “intimate and heartfelt memoir” about his life.
The memoir, published by Penguin Random House, will be the “definitive account” of the Duke’s “experiences, adventures, losses, and life lessons”.
The “wholly truthful” account will be ghost-written by Pulitzer Prize-winner JR Moehringer.
The Duke of Sussex added in promotional material: “I’ve worn many hats over the years, both literally and figuratively, and my hope is that in telling my story — the highs and lows, the mistakes, the lessons learnt — I can help show that no matter where we come from, we have more in common than we think.”
He continued: “I’m deeply grateful for the opportunity to share what I’ve learned over the course of my life so far and excited for people to read a first-hand account of my life that’s accurate and wholly truthful.”
However, one publishing source has claimed to US tabloid Page Six that the release date is “up in the air”.
Another anonymous source, in an unconfirmed claim, told the publication: “I have heard that Harry has some truth bombs in his book that he is debating on whether to include or not.
“So this [push back is] no surprise if he needs more time to work on the book.”
In a conflicting, unconfirmed account, a publishing source told The Sun last month: “The manuscript has been finished and gone through all of the legal processes.
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Their legal and advisory teams are none the wiser, the publication added.
A prominent royal journalist said on Wednesday that the memoir, and the speculation around it, had “eroded trust” between the Firm and the Duke and Duchess of Sussex.
Former BBC correspondent Jennie Bond referenced the impact of the explosive 2021 interview with US chat show host, Oprah Winfrey.
Ms Bond told GB News: “There is very little trust after the Oprah interview, particularly between William and Harry and other members of the Royal Family.
“They don’t know what bombshell is going to come next.”
She added: “Trust is something that is very important in royal circles.”
“There aren’t very many people they can trust.
“Discretion is everything and Meghan and Harry have demonstrated that they’re no longer willing to be traditionally discreet about what goes on behind palace walls.”