TOKYO - Japan's new Prime Minister Naoto Kan, is a former grassroots civic activist who is now pushing for fiscal belt-tightening.

Kan, 63, a former leader of the Democratic Party of Japan, achieved popularity when as health minister he exposed government culpability in a scandal over HIV-tainted blood in the mid-1990s.

Nicknamed "Ira-Kan" or "Irritable Kan" for his fiery temperament, he also has a populist flair and wields a lot of influence in the center-left party he helped create over a decade ago with outgoing Prime Minister Yukio Hatoyama.