Queen Camilla was allegedly confronted by Princess Anne over her new title at a tense Coronation dinner with other members of the Royal Family.
The Princess Royal is alleged to have told her sister-in-law that her title is Queen Consort and not Queen, according to Princess Diana's dressmaker, David Emanuel.
He claimed that the topic of Camilla's new title is "highly charged" and that "a lot of people" are "unhappy" that she will be referred to as Queen rather than Queen Consort.
The King's wife was reportedly confronted by Anne as the designer said the "whole situation" is "very difficult" amid claims that not everyone accepts Camilla's new title.
Speaking to Dan Wootton on GB News, Mr Emanuel, who designed Princess Diana's wedding dress in 1981, said: "I heard that there was a Coronation dinner with which obviously the King and Camila were there, and apparently the Princess Royal said, 'You're not Queen, you're the Queen's consort'."
He added: "I understood from Her Majesty the Queen, she said she should be Queen Consort. Now suddenly she's now going to be Queen.
"And it's very difficult because a lot of people have told me they were unhappy about it."
During the Coronation, Princess Anne will feature in the procession as the prestigious "Gold-Stick-in-Waiting", a position historically handed to a person entrusted with the personal safety of the sovereign.
As a "personal aide-de-camp" to His Majesty, Anne will travel on horseback behind the new King and Queen after they are crowned at Westminster Abbey on May 6.
As Charles and Camilla ride in the Gold State Coach back to Buckingham Palace, Anne will lead the larger procession featuring 6,000 armed services personnel.
The privilege dates back to the 15th century in Tudor times, when two officers - a Gold Stick and a Silver Stick, were placed close to the sovereign to protect him or her from danger.
One of the guests at the Coronation is Camilla's former husband Andrew Parker Bowles, who was married to her for 22 years from 1973 to 1995.
Friends of the 83-year-old said he is "a bit of a rogue" and "very naughty with women", according to a source who spoke to The Times.
Andrew also once had a brief romance with Princess Anne, but the two reportedly remain close friends.
His grandchildren Freddy, 13, and twin boys Gus and Louis, also 13, will carry the train of Camilla's robes.
According to the newspaper, a friend of the Parker Bowles family said: "They are joined at the hip. He arranges so much for her. They have lunch together the whole time. He’s right in there. He was always, and still is, Camilla’s co-conspirator."
