Palace responds to claim about King Charles after Princess Diana's death

Buckingham Palace has issued a rare response to a claim made in an upcoming book by Princess Diana's brother, Charles Spencer.

The Daily Mail published a preview of Spencer's book on Tuesday that includes an allegation involving King Charles III in the days after Diana's death in 1997.

Spencer alleges that during a disagreement over Diana's funeral arrangements, Charles, who was then the Prince of Wales, told him, "rest assured, we'll forget her soon enough," according to the excerpt.

A Buckingham Palace spokesperson responded to the claim in a statement to ABC News on Wednesday.

"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 colour memory in ways others do not recognise, even many years after such a loss," the statement read.

Diana, Princess Of Wales, Talking To Her Husband, During A Visit To The British Embassy. The Princess Is Wearing A Taffeta And Lace Gown With A Scalloped Neckline Designed By Murray Arbeid With Queen Mary's Diamond And Pearl Tiara, A Present From The Queen.Tim Graham Photo Library via GetThe response is unusual for Buckingham Palace, which typically does not comment on books or reports about members of the royal family.

The palace also remained publicly silent following the release of Prince Harry's 2023 memoir, "Spare," despite the book containing numerous claims about Charles and other members of the royal family.

Diana was killed on Aug. 31, 1997, after the car she was riding in crashed in Paris. She was 36 at the time.

Spencer, Diana's younger brother, is an author and historian who delivered the eulogy at her funeral. His upcoming book, "Swan Song: Diana, My Sister," tells the story of Diana's life from his perspective as her brother.

ABC News has reached out to Spencer's publisher, Penguin Random House, for comment.