Buckingham Palace has strongly rejected a claim by the brother of the late Princess Diana that King Charles III said his former wife would soon be forgotten after her death.
In a new book, Charles Spencer describes the difficult days following Diana's death in a car crash in Paris in 1997 at the age of 36.
Spencer claims he argued with Diana's former husband, then Prince Charles, over plans for Prince William and Prince Harry, who were 15 and 12 at the time, to walk behind their mother's coffin during her funeral procession.
Spencer says he told Charles that Diana would not have wanted her sons to go through such an ordeal. He alleges that Charles replied: "Rest assured, we'll forget her soon enough."
Spencer also accuses Charles of showing "contempt" toward Diana and says the then-prince sounded "elated" after her death.
The Daily Mail has published extracts from Spencer's book, "Swan Song: Diana, My Sister," which is due to be released next week.
Buckingham Palace issued an unusually strong statement late Wednesday in response to the claims.
"While we do not comment on books as a matter of principle, 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 palace said.
Ingrid Seward, editor-in-chief of Majesty magazine, described the statement as "very strong."
"I can't think of another occasion … in the recent history of royal communications which has been as stark as this one," she said, adding that it was clearly issued with "a great deal of feeling."
Tensions between the royal family and the Spencer family after Diana's death have been widely discussed and portrayed in the film "The Queen" and the television series "The Crown."
The royal family faced criticism at the time for being slow to respond to the public's grief over Diana's death. Her ability to connect with ordinary people highlighted a more personal side that many felt was missing from the wider royal family.
Prince William and Prince Harry later adopted a more openly emotional approach, while King Charles has also become more publicly expressive in recent years.
Charles, then 32, married 20-year-old Lady Diana Spencer in a lavish ceremony at St. Paul's Cathedral in 1981. They separated in 1992 and divorced in 1996.
Charles Spencer, the 9th Earl Spencer, has long criticized the royal family's treatment of his sister.
In a widely discussed eulogy at Diana's funeral, Spencer promised that her "blood family" would preserve her "imaginative and loving" legacy while raising her two sons. The speech was widely viewed as criticism of the royal family.
"I feel that the Spencers and the royals are just never going to become friends again, as they were centuries ago," Seward said. "They were very close, but I don't think they're going to become friends again in any hurry."
George Gross, a royal historian at King's College London, questioned why Spencer had chosen to revisit the painful period publicly.
"We're dealing with somebody's death," he said. "It is very sad at the root of it, and I have to ask some questions as to why a brother at this point is going over all of that again in a book. I think the public know the answer to that."