Former Democratic Party of Japan chief Ichiro Ozawa and 49 other DPJ lawmakers on Monday bolted from the DPJ, which Mr. Ozawa had helped come to power by leading it to a victory in August 2009 Lower House election.

The 50 lawmakers — 38 Lower House members and 12 Upper House members — oppose the bills for the so-called unified reform of the tax and social security system, the pillar of which is a bill to raise the consumption tax rate from the current 5 percent to 8 percent from April 2014 and to 10 percent from October 2015. Mr. Ozawa and his comrades are expected to form a new party.

The tax-raise plan in the midst of long deflation carries the danger of wrecking the economy and thus decreasing total tax revenues. The bills before the Diet are also weak in reforming the social security system itself.