In a tweet on Wednesday, Mr Spencer shared his late sister’s opinion of the former president.
“Surprised to hear that Donald Trump is apparently claiming that my late sister Diana wanted to ‘kiss his a***’, since the one time she mentioned him to me – when he was using her good name to sell some real estate in New York – she clearly viewed him as worse than an anal fissure,” he wrote.
The former president claimed that his new book will feature letters from the late Queen Elizabeth II, the late Princess Diana, Russian president Vladimir Putin, North Korean leader Kim Jong Un, multiple former US presidents, 2016 Democratic rival Hillary Clinton, Oprah Winfrey and other celebrities.
The book titled “Letters To Trump” is due to be released on 25 April.
In an article published in far-right Breitbart News this week, Mr Trump said: “I knew them all –and every one of them kissed my a**, and now I only have half of them kissing my a**.”
Mr Trump has earlier said that he could have “nailed” Princess Diana.
Mr Trump had made the comments in a 1997 interview, months after the car crash that killed Princess Diana, with radio host Howard Stern. The remark was unearthed during the 2016 presidential campaign.
Celebrities like Oprah Winfrey and Jay Leno have responded to the use of their personal letters in Mr Trump’s book.
“Jay did not release, nor authorise any use of any letter to Trump,” a representative of Leno told Newsweek.
However, the publishing company behind the former president’s book has said that there had been “actual or implied” permission from the letter senders who are private individuals.
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