The clarification comes after Morgan threatened legal action over passages in Spencer's book, which explores the life and death of his older sister.
In the memoir, Spencer recalls calling Morgan to tell him that he was not welcome at Diana's 1997 funeral. Spencer maintains that Morgan was "surly and annoyed" during the conversation.
However, Spencer has acknowledged an error in his explanation of what may have caused Morgan's reaction. The book incorrectly states that Morgan was editor of the Daily Mirror when the Mirror Group published photographs of Diana exercising at a gym in November 1993.
Morgan was actually working at The Sun at the time and did not become editor of the Daily Mirror until 1995.
A statement issued on Spencer's behalf said his account of the conversation was accurate, including his recollection that Morgan appeared annoyed when Spencer personally informed him that he would not be attending Diana's funeral.
The statement clarified that Spencer had assumed Morgan's reaction was connected to the publication of the photographs while he was editor of the Daily Mirror. Spencer now acknowledges that assumption was incorrect.
"As an historian, accuracy is important to Earl Spencer. He therefore wishes to clarify that his assumption was incorrect," the statement said, adding that Spencer apologized to Morgan for the error.
The disputed passage will reportedly be corrected in the second edition of Swan Song.
Morgan, however, said the apology would not resolve the dispute and confirmed that he intends to continue with legal action against Spencer and publisher Penguin.
Morgan also disputes Spencer's account of their phone conversation. In a post on X, he said he was not "surly nor annoyed" but was respectful toward Spencer and his family. He said his version of events was recorded in his diaries, The Insider.
The disagreement is the latest controversy surrounding Spencer's memoir. Buckingham Palace has also challenged a separate claim in the book concerning King Charles and Diana's death. Spencer has continued to stand by that account.
Speaking to PEOPLE, Spencer said he approached the memoir both as a historian and as Diana's brother, emphasizing that his focus was on recording what he believes to be the facts.
He added that Diana remained the central focus of the book despite the attention surrounding its revelations.
