Prince Harry has accused his brother, Prince William, of physically attacking him during an argument about his marriage to Meghan, The Guardian reported on Thursday.

The British newspaper said it had obtained an advance copy of Harry’s new memoir, «Spare», due to be published next Tuesday, January 10.

Harry says in the book that William «threw him to the ground» during an argument at the Sussexes’ London home in 2019 when the brothers’ relationship skyrocketed, The Guardian reports.

The upcoming book seems set to intensify Harry and Meghan’s feud with the royal family, as the couple seek to present their side of the story pitting Hollywood celebrities against the century-old British institution.

NBC News has yet to obtain or view a copy of the book. Representatives for Prince Harry declined to comment on the record, and publisher Penguin Random House did not immediately respond to requests for comment.

The book’s title is an apparent reference to Harry being a real «spare», not first in line. William, Prince of Wales, is next in line.

According to The Guardian, the book describes «intensely private scenes and conversations» covering everything from Harry’s early childhood to his marriage to former actress Meghan Markle. This includes details about Harry’s relationship with his mother, Princess Diana, who died in a car accident in 1997, his father, now King Charles, and his late grandmother, Queen Elizabeth II.

Kensington Palace, which represents Prince William, and Buckingham Palace, which represents King Charles, declined to comment on the allegations made in the book.

The Guardian article focuses on an alleged attack on Harry and Meghan’s former London home of Nottingham Cottage in the grounds of Kensington Palace in 2019.

Prince Harry reportedly says in the book that his brother William complained about Meghan, calling her «difficult», «rude» and «abrasive».

Then the confrontation escalated and the brothers yelled at each other and insulted each other, says the newspaper reporting the book. Harry reportedly says that he was afraid of his brother, who was furious and followed him around the house. Harry writes that William then grabbed him by the neck and ripped him open before throwing him to the ground, The Guardian reports.

“I landed in the dog bowl, which split under my back, the pieces cut me. I stood there for a moment, stunned,» Harry writes in the leaked passage from the book published by The Guardian. Harry reportedly told his sister to leave, which he did after initially urging Harry to hit him back, according to the newspaper.

William later returned and apologized, the newspaper reports, although the excerpt says he suggested Harry not tell Meghan about the alleged altercation.

“’You mean you attacked me?’ Harry writes back, according to the newspaper. “’I didn’t attack you, Harold,’” she says William reportedly called her back.

Harry writes that he initially only spoke to a therapist about the alleged incident, according to the leak. But when Meghan noticed «scratches and bruises» on her back, he told her what had happened, the Guardian book quotes.