TOKYO — Japan’s extreme sensitivity over its royal family was laid bare yesterday when it reacted furiously to an unauthorized biography of its most famous — and controversial — princess.

Lodging a formal protest with the government of the author’s native Australia, the Tokyo government described the account of the life of Princess Masako as “disrespectful and distorted” and demanded an apology.

The rare intervention was delivered via the Japanese embassy in Australia.

The Australian author and former Tokyo journalist Ben Hills refused to apologize yesterday and accused Japan of attempting to censor his book.

Princess Masako, the 43-year-old wife of Crown Prince Naruhito, has been suffering from a depressive illness that has kept her from performing almost any royal duties since December 2003.

Mr. Hills calls her “a prisoner of the Chrysanthemum Throne” in the subtitle of his book and attributes her illness to the treatment she has endured since marrying into the royal family in 1993.

Royal protocol has denied the princess, who was educated at Oxford and Harvard, the kind of high-profile role that she and her husband clearly intended.

Instead, she has been allowed on only a few official visits overseas and has endured intense pressure to produce a son to secure the line of succession.