Earl Spencer's war with King Charles takes fresh turn as Palace braces for new interview

Princess Diana’s brother insists he is “not bitter” towards King Charles despite wild claims in his book triggering anger from Buckingham Palace .

A war of words broke out in the wake of Earl Charles Spencer’s allegation Charles told him Diana would be forgotten “soon enough” after her death. Earl Spencer accused the then Prince Charles of launching into a furious tirade during a phone call in the days after the princess was killed in a Paris car crash, alongside her lover Dodi Fayed, in 1997.

However, in a new interview set to air on Sunday in the US, the aristocrat insisted: “I’m absolutely not bitter. I can tell you. If I was bitter, this book would be... more bitter.”

Asked if he has any resentment towards the King or the royal family , including the late Queen, he added: "I'm not really in the business of resentment. I'm at the stage in my life where the past is the past, and some of it's worth recording.

"But I don't hold resentments, primarily because I don't think it's good for the person to do that themselves. I've let a lot go. I'm not a vengeful, resentful, person. I'm just an eyewitness to history."

The Earl, 62, gave a sitdown interview to the US TV station CBS at his home at Althorp, Northamptonshire, ahead of the publication of his new book Swan Song: Diana, My Sister, on Tuesday. The publication of extracts this week led to Buckingham Palace issuing a strongly worded rebuke just over an hour after the Earl’s claims were made public.

The extraordinary royal statement denied the claim and said the King is “mindful that the pain of fraternal grief can cloud reason, affect judgement and colour memory in ways others do not recognise, even many years after such a loss”. In the new memoir, Earl Spencer also claims Charles had “sounded giddily elated” when he called him after Diana’s death. And he even alleges that he sounded like he had won the lottery.

The book also includes the Earl claiming he hung up the phone on the then future King after telling him how he strongly disagreed with the royals' decision to have princes William and Harry – then aged just 15 and 12 – walk behind their mother’s coffin. He also claims in the tome that a lack of obvious care for Prince Harry at his mother’s funeral allowed him to “spin out of control” and that immediately after Diana's funeral he was told Queen Elizabeth had offered to restore his sister's Her Royal Highness title, which he rejected.

Asked by CBS Senior Foreign Correspondent Mark Phillips during the interview if he has any remaining relationship with King Charles , Earl Spencer said: "No, I don't actually. Look, he came into my life as a brother-in-law and that relationship ended.

"And so, you know, he's still my King. I respect the Crown, and that's it, but there's no personal relationship. He's a former brother-in-law to me, really, and he's my monarch and that's it." Earl Spencer added: "I always think people are amazed by how little I follow the royal family 'cause it's just not me. I have so many interests, but I'm not being rude about them...