Charles Spencer has given his first interview after a week of making explosive claims about Britain's royal family.
The accusations have preceded a war of words with Buckingham Palace.
Princess Diana's brother defended himself in the exchange with the BBC, broadcast on Friday evening.
Princess Diana's brother has stood by explosive claims about Britain's royal family, insisting he is "telling the truth" and suggesting the king is "embarrassed".
Charles Spencer's bombshell accusations are contained in his soon-to-be-released memoir, excerpts of which have been published this week.
The most disparaging allegations Earl Spencer has made relate to phone calls he says he had with Charles around the time of Diana's 1997 death in a car crash.
Charles and Diana's divorce had been finalised the previous year.
Earl Spencer accused the Charles of sounding "giddily elated" during a conversation on the night Diana died, and also of saying "we'll forget her soon enough" several days after the crash.
In an interview with the BBC broadcast on Friday evening, local time, Earl Spencer defended himself.
When pressed about his claims that King Charles — who was not on the throne at the time — had told him "we will forget" about Diana, Earl Spencer said: "I've only ever had two calls on the line with Prince Charles at any stage of my life."
In another claim published Friday, Earl Spencer said he worried about the level of care given to Charles and Diana's youngest son, Prince Harry, on the day of the funeral.
On Thursday, Dickie Arbiter rubbished the claims made in the book.