Beijing-baiting Tokyo governor Shintaro Ishihara, whose plan to buy disputed islands ignited a smouldering row with China, on Thursday branded Japan's pacifist constitution "ugly" as he launched a bid for national power.
The outspoken 80-year-old Ishihara said he was giving up his role at the helm of one of the world's largest cities to form his own political party ahead of expected general elections.
"As of today, I will resign as Tokyo governor," Ishihara told a news conference, brandishing a white envelope. "I'm planning to return to national politics. I want to do so by forming a new party with my associates."
Observers say elections -- which must be held within the next year, but are seen likely to come sooner -- will probably not produce a clear result, giving smaller parties a powerful voice in the expected coalition-building.
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 Japanese politics, novelist-turned-politician Ishihara objects, among other things, to Article 9 of the constitution, which bars Japan from waging war.
Ishihara, who has been an irascible presence in the national conversation for decades, 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.
On Thursday Ishihara said he would "cooperate and collaborate" with Hashimoto's group, while the Osaka mayor said he would "have many discussions" with Ishihara, Kyodo reported.
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.