A report into bullying allegations against Meghan Markle are still being investigated after three months - and a report has been delayed until next year, it is claimed.
Buckingham Palace is investigating allegations that the Duchess of Sussex bullied two senior staff.
But it could be some time before the final report is released, The Times reports.
Insiders told the newspaper that the investigation is "ongoing", .
The allegations surfaced publicly in March this year, which the palace saying it was "concerned" at reports staff had been bullied.
It has been branded a "calculated smear campaign" by the Sussexes, who fiercely deny any wrongdoing.
The couple's former communications chief, Jason Knauf, reportedly submitted an email alleging unacceptable behaviour by the Duchess in 2018.
It is claimed to have been the spark that prompted Prince William to separate his household from the Sussexes.
Historian Robert Lacey claims an angry phone call between the brothers ended in Harry hanging up as they clashed over claims the Duchess of Sussex left at least one worker suffering post traumatic stress disorder (PTSD) due to the "toxic" environment.
William "went ballistic" when he heard the allegations, and later instructed his private secretary, Simon Case, to begin dividing their households "immediately", it is claimed.
In an extract from Lacey's book, Battle of Brothers, published by The Times, a friend claimed: "William threw Harry out."
The younger brother, the book says, was upset that William had considered the claims credible.
According to Lacey, the brothers' joint communications secretary, Jason Knauf, had decided to speak up for staff after hearing claims of mistreatment by the Duchess of Sussex.
He compiled a dossier outlining allegations, which was sent to the Duke of Cambridge's private secretary.
William, who "personally liked" all the staff alleged to have been mistreated by Meghan, came to believe that the former actress was "fundamentally hostile to the royal system", Lacey wrote.
He claimed that the second-in-line to the throne regarded staff as "colleagues to be cherished and for whom he was responsible", meaning he was "appalled" by the contents of the dossier.
The 2018 document - which Harry and Meghan have refuted - claimed the Duchess had bullied two PAs out of their jobs in the previous year.
It also claimed that Meghan seemed intent on "always having someone in her sights", and Knauf said he had received “report after report” from people who witness "unacceptable behaviour” by Meghan towards a member of staff.
In a statement in March, Harry and Meghan said: "We are disappointed to see this defamatory portrayal of The Duchess of Sussex given credibility by a media outlet.
"It’s no coincidence that distorted several-year-old accusations aimed at undermining The Duchess are being briefed to the British media shortly before she and The Duke are due to speak openly and honestly about their experience of recent years.
"In a detailed legal letter of rebuttal to The Times, we have addressed these defamatory claims in full, including spurious allegations regarding the use of gifts loaned to The Duchess by The Crown.
"The Duchess is saddened by this latest attack on her character, particularly as someone who has been the target of bullying herself and is deeply committed to supporting those who have experienced pain and trauma.
"She is determined to continue her work building compassion around the world and will keep striving to set an example for doing what is right and doing what is good."