Prince Harry was physically attacked by his older brother Prince William during an argument over his wife Meghan, according to an excerpt from his memoir leaked days before its publication.

In the latest salvo in the brothers' bitter feud, Harry says the alleged incident came after the heir to the British throne called Meghan "difficult", "rude" and "abrasive".

Details of the row come as the British royal family braces for the publication on Tuesday of Harry's book "Spare".

The spat in 2019 – the year after Harry and Meghan married – allegedly saw William tackle his younger brother to the ground as they continued to argue.

"He grabbed me by the collar, ripping my necklace, and he knocked me to the floor. I landed on the dog's bowl, which cracked under my back, the pieces cutting into me," newspapers quoted Harry's book as saying.

Harry then told his older brother to leave. William looked "regretful, and apologised", Harry recalled, according to the reports.

Quoting from the exchange between the two princes in the book, the reports claimed William turned and called back: "You don't need to tell Meg about this."

"You mean that you attacked me?" said Harry.

"I didn't attack you, Harold," William responded, seeming to use a nickname for his brother.

The revelation follows a string of other broadsides in the wake of Harry and Meghan's decision to quit royal duties in Britain in early 2020. (AFP)