New Delhi, Sept. 21 -- Princess Diana's brother Charles Spencer has spoken out after Buckingham Palace issued a rare response to claims in his forthcoming memoir, Swan Song: Diana, My Sister. Spencer accused King Charles of "gaslighting" him and said he was shocked by the Palace's reaction.

Speaking in an interview with ABC News' Maggie Rulli for Good Morning America, Spencer addressed the statement issued by Buckingham Palace after excerpts from his book were published ahead of its 22 September release.

"Well, it's not every day you're gaslit by a king, but I was really upset with that because I thought it was very, not only condescending, but not straight," Spencer said. "What I said is straight and true. And what did they come back w...