Beijing-baiting Tokyo governor Shintaro Ishihara, whose bid to buy disputed islands ignited a smouldering row between Japan and China, resigned Thursday to start his own national political party.
The outspoken 80-year-old Ishihara said Japan's pacifist post-war constitution was "ugly" and needed to be reframed.
"As of today, I will resign as Tokyo governor," Ishihara told a news conference, brandishing a white envelope, in an announcement that took Japan's political and media establishment by surprise.
"I'm planning to return to national politics. I want to do so by forming a new party with my associates."
Newspaper reports earlier Thursday said Ishihara wanted to forge a grouping big enough to rival the two largest established parties before an expected general election.
But they had made no mention of the four-term Tokyo governor stepping down from a position he has held for more than 13 years.
Ishihara, whose pronouncements on history have irked China -- he once denied the 1937 Rape of Nanking ever happened -- said he saw much wrong with national politics.
"There are several contradictions, big contradictions, which we hope the state itself will solve," he told reporters.
"One contradiction, bigger than anything, is the Japanese constitution, which was imposed by the (post World War II US) occupying army, and is rendered in ugly Japanese."
Like many on the right of politics, novelist-turned-politician Ishihara objects, among other things, to Article 9 of the constitution, which bars Japan from waging war.
Ishihara, an irascible voice for decades in Japan's national dialogue, will co-opt members of the tiny right-wing Sunrise Party for his new venture, the daily Yomiuri Shimbun reported.
He will also seek to join hands with the mayor of Osaka Toru Hashimoto, a straight-talking maverick whose recently-formed Japan Restoration Party has ambitions to seize control of the powerful lower house.
Embattled Prime Minister Yoshihiko Noda is under pressure to call a general election after telling opposition parties he would go to the polls "soon" if they supported his unpopular bill to double the consumption tax.
His own approval ratings are low and his ill-disciplined Democratic Party of Japan is likely to be given short shrift by voters disillusioned with its three years in office.
But the establishment Liberal Democratic Party -- to which Ishihara once belonged -- has largely been unable to capitalise on Noda's poor standing and many commentators say a national ballot would produce stalemate.
Observers suggest smaller parties could play a significant role in a post-election landscape in which coalition-building will be the order of the day.
Ishihara's move Thursday comes months after he roiled often-tense Japan-China ties by suddenly announcing he wanted to buy a group of uninhabited but strategically important islands in the East China Sea.
He amassed 1.4 billion yen ($17.5 million) in public donations for the metropolitan government to acquire the Senkakus, which are controlled by Japan but claimed by China as the Diaoyus.
That forced Noda to step in and outbid him in what ministers have maintained was an attempt to avoid an escalation of the long-running dispute.
Nationalists on both sides staged island landings before the government completed its purchase of three of the five islands in the chain -- it already owned a fourth and leases the fifth -- on September 11.
Beijing reacted furiously and tens of thousands of protesters poured onto the streets in cities across China, some vandalising Japanese business outlets.
Japan's exports to China, its biggest trading partner, tumbled 14.1 percent last month, with some saying the row triggered a fall-off in demand for Japanese-branded products.
On Thursday four Chinese government ships spent several hours in waters around the islands, Japan's coastguard said, the latest seaborne confrontation between official vessels from Asia's two largest economies.
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