King Charles III issued a critical response to a forthcoming memoir by Princess Diana’s brother, Charles Spencer, warning that grief can cloud judgment and memory.

Spencer, the 9th Earl Spencer, alleged in his bombshell book, “Swan Song: Diana, My Sister,” that the monarch vowed his ex-wife would be forgotten “soon enough” shortly after she died in a 1997 car crash at the age of 36.

The author described the alleged remark as the monarch’s “pent-up contempt for Diana, and his horror that the world was so bowled over by her death,” per the Daily Mail.

King Charles III responded to allegations in a forthcoming memoir by Princess Diana’s brother. (Seen above: Charles and Diana in 1990.) Getty Images

In his book, “Swan Song: Diana, My Sister,” Spencer, the 9th Earl Spencer, alleged that the monarch claimed his ex-wife would be forgotten “soon enough” after her 1997 death. (Seen above: Spencer.) WireImage

A Buckingham Palace spokesperson, however, warned that the loss of the Princess of Wales could have muddled Spencer’s memory.

“His Majesty is mindful that the pain of fraternal grief can cloud reason, affect judgment and color memory in ways others do not recognize, even many years after such a loss,” the rep told Page Six.

Diana and Charles, now 77, tied the knot in 1981 and divorced in 1996, the year before she tragically died at the age of 36 in a car crash after being chased around Paris by paparazzi.

Spencer described the comment as Charles’ “pent-up contempt for Diana, and his horror that the world was so bowled over by her death.” (Seen above: Charles in July.) Getty Images

A rep for Buckingham Palace warned that Spencer’s recollection might be muddled. (Seen above: Diana and Charles in 1991.) Getty Images

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The late royal was with her driver, Henri Paul, and her boyfriend, Dodi Fayed, when the fatal crash occurred in the Pont de l’Alma tunnel.

Elsewhere in the book, Spencer reflected on Diana’s funeral at Westminster Abbey in London on Sept. 6, 1997.

He alleged that days before, he received a call from the now-late Queen Elizabeth II’s aide, saying that Diana and Charles’ sons, Prince William and Prince Harry, who were 15 and 12 at the time, respectively, would not be participating in the funeral procession.

“His Majesty is mindful that the pain of fraternal grief can cloud reason, affect judgment and color memory in ways others do not recognize, even many years after such a loss,” the rep told Page Six. (Seen above: Diana and Charles.) Tim Graham Photo Library via Getty Images

Diana and Charles (seen here in 1983) married in 1981. Toronto Star via Getty Images

“That’s not going to happen,” Spencer claimed he told the aide.

Ultimately, the boys participated in the procession with Spencer, Charles and the now-late Prince Philip.

In the book, Spencer detailed Charles and Diana’s relationship from their royal wedding at St. Paul’s Cathedral in London to the downfall of their marriage.

The exes’ marriage was plagued by extramarital affairs on both ends, with Charles’ being with his now-wife, Queen Camilla.

Camilla and Charles eventually married in 2005 following her divorce from Andrew Parker Bowles in 1995.

The exes (seen here in 1987) divorced in 1996. Getty Images

Diana (seen here in 1992) died in 1997 at the age of 36. Getty Images

An insider told Page Six that Harry was aware of the allegations in Spencer’s book, and the claims “didn’t come as a shock.”

The Duke of Sussex spoke with his uncle about the book when the latter stopped by the Spencer ancestral estate, Althorp, in July, when Harry was visiting the UK with his wife, Meghan Markle, and their kids, Prince Archie and Princess Lilibet.

Spencer’s book will be released on Sept. 22.