Japan’s Crown Prince Naruhito used a surprise television appearance today to deliver an extraordinary attack on the ways of the Imperial Palace.

Seasoned Japanese royal family watchers said that Prince Naruhito offered the strongest hint ever that he blames the Imperial Household Agency for his wife’s continuing ill health.

He pointed to times when Princess Masako "has been denied her individuality", and said that her decade-long effort to adjust to life in the Imperial family had worn her out.

His comments, part of a rare press-conference that was itself a sharp break with tradition, come just days away from a three-country visit to Europe.

Significantly, it is a trip he will be making without the company of his 40-year old wife, who has cancelled all official engagements since December and remains in seclusion suffering from stress-related ill health.

Using Japanese terms that virtually never appear in imperial statements, Prince Naruhito repeatedly said what a shame it was that she would not be joining him.

He regretted that he was leaving her in Japan and said he was doing so with "painful reluctance". Adding further poignancy to her cancelled travel plans was his explanation that a key part of Princess Masako’s life that had been denied her was the ability to travel outside Japan.

Prince Naruhito reminded his audience that before she married into the imperial family, his cosmopolitan, Harvard and Oxford-educated wife had been a diplomat.

The Prince’s thinly-veiled criticism of palace life fits in with speculation over the historical ill-health of his mother, Empress Michiko, who became the first commoner to marry into the world’s oldest royal family in 1959.

It is an open secret in Japan that the Empress was driven to a nervous breakdown by the pressures of imperial palace life.

Prince Naruhito concluded with vaguer hints about the thorny succession issue, and whether or not Japan will change its rules to allow his daughter, Princess Aiko, to one day sit on the Chrysanthemum throne.

The still unresolved matter is thought to be yet another source of stress for Princess Masako, and the Prince said that he would "continue my efforts to create an imperial system suited for the new age."

Princess Masako’s prolonged ill-health has been a matter of major public speculation in a country where the imperial family is a focus of massive popular interest.

The Prince’s comments follow a surprisingly frank statement made on his 44th birthday in late February. At that time he said that Princess Masako had been made ill by the relentless pressure to produce a male heir, and appealed to the media to allow her to rest.

Significantly, he also asked the Imperial Household Agency for its co-operation.

Since then, however, there has been little word of any improvement in Princess Masako’s health. She has spent most of 2004 convalescing in a villa in the rural prefecture of Nagano with her mother and 2-year old daughter.

She returned to Tokyo late last month at the beginning of Japan’s "Golden Week" of national holidays, reportedly concerned that the town of Karuizawa, where she was staying, would be flooded with concerned well-wishers travelling from across the country.