Earl Spencer has rejected claims that his new memoir, "Swan Song: Diana, My Sister," is intended as a "hit piece" on King Charles, asserting that he "stands by the truth" and wrote the book in honor of his late sister.

In his first live television interview to promote the memoir, which was published on Tuesday and is being serialized by the Daily Mail, Spencer addressed the controversy surrounding the book's inclusion of an allegation that Prince Charles, now King Charles, told him in the days following Princess Diana's death: "We will forget her soon enough."

Buckingham Palace issued an unprecedented statement in response, with royal aides questioning the veracity of Spencer's account and suggesting that grief can "cloud reason, affect judgment and colour memory."

However, Spencer, speaking on ITV's Lorraine, described the King's reported comment and the Palace's subsequent statement as "classic gaslighting." He maintained that he was not rattled by the furore, stating, "So what they do is 'ooh, maybe his mind's not right to remember these things because of the distance of time and grief.' No one said the King didn't say that, because he did and he couldn't say that."

Spencer reiterated his commitment to his account, saying, "I stand by the truth and that's the way it is. I knew when I took this on that it would have a controversial effect, but it doesn't matter because it's for Diana and I'd do anything for her."

He further suggested that if his intention were to create a damaging narrative, he could have done so more forcefully. "If I wanted to do a hit piece on the Royal Family, I could do that," Spencer said. "But that's not my job - my job in this book was to celebrate Diana. By doing that, other people are not going to come off as well as they might want to, and there's a huge power dynamic in this country - Buckingham Palace has journalists who basically take dictation from them, and that happens, it's realistic, I knew it was going to happen."

The memoir also reportedly details an argument between Charles and Spencer concerning the decision for Princes William and Harry, then aged 15 and 12, to walk behind their mother's coffin during her funeral procession. Spencer claimed he argued against it, believing Diana would not have wanted her sons to endure such a public ordeal, but was overruled. He told Lorraine that he cannot think of anyone who believes it was a good decision, recalling the walk as "agony" for the young princes.

Spencer also addressed a dispute with Piers Morgan over claims made in the book about the former newspaper editor. Spencer had written that Morgan "snarled with annoyance" when informed he was not invited to Diana's funeral and implied Morgan might feel guilt over photos of Diana published in 1993, when Morgan was not the editor of the Mirror. Morgan has reportedly threatened legal action over alleged inaccuracies. Spencer acknowledged a "small error" regarding Morgan's timeline and stated he had apologized, with the correction to be included in the book's second edition.

Spencer stated he had not discussed the book with Prince Harry or Meghan Markle, despite their previous stay at his Althorp estate. He mentioned that his wife, Cat Jarman, was the only person he had discussed the book with prior to its publication.

Reflecting on the book's reception, Spencer said he anticipated controversy and drew inspiration from Diana's own resilience in facing intense press scrutiny, which he noted was "way worse than I'm getting this week."