Japan's Prime Minister Yoshihiko Noda (C) arrives at his ruling Democratic Party of Japan board members' meeting at the parliament in Tokyo on July 2, 2012. (Yuriko Nakao/Reuters)

The chief rival to Japan’s prime minister tried his best to wreak havoc Monday by quitting the ruling party to protest a tax increase and encouraging other lawmakers to do the same.

But the defection of power broker Ichiro Ozawa and 49 of his loyalists failed to strike a critical blow to Prime Minister Yoshihiko Noda, whose party emerged from this long-anticipated rebellion with its majority intact. Noda now commands a smaller party but also a more unified one, political experts here say, and no longer must he worry about placating the most vocal critic of his policies.

Ozawa, 70, is perhaps Japan’s most divisive politician, a master of Tokyo’s backroom deal-making, and he had hoped to spark a larger defection, which would have been more difficult for Noda to shrug off. Had 55 or more ruling-party members in the lower house handed in resignations, the Democratic Party of Japan (DPJ) would have lost its majority and Noda would have been susceptible to a no-confidence vote that might have kicked him out of office.

Instead, only 37 lower-house members followed Ozawa, joining 12 from the upper house. Ozawa plans to form a splinter party this month, Japanese media said, but that fledging group — even after an anticipated merger with the tiny Kizuna Party — would not have enough members to even submit a no-confidence vote.

“Ozawa’s group will be 40 or 50 members, only a small group, so even if he tries to make something happen, it won’t work,” said Harumi Arima, a Japanese political pundit and a former parliamentary aide. “He won’t have enough members. The DPJ will continue to cooperate with the [opposition] and pass bills.”

Ozawa, known as a skilled campaign strategist, is largely credited with masterminding the DPJ’s rise to power in 2009, when it ended the Liberal Democratic Party’s half-century of near-uninterrupted rule. But Ozawa failed in his attempt to become prime minister, and during Noda’s 10-month-old administration, he became an outspoken critic of a plan to double the consumption tax.

Noda says the increase is necessary to fund Japan’s escalating social security costs and curb its massive debt. But Ozawa said the proposal breaks a promise that the DPJ made three years ago as part of its party manifesto.

“The tax hike would be a betrayal against the people,” Ozawa said.

Noda secured support last month from opposition parties for the tax increase, and a series of bills easily passed the lower house last week — despite objections from Ozawa and his supporters. The consumption tax increase legislation will become law if, as expected, it clears the upper house in a month or two.

The proposal calls for doubling the consumption tax to 10 percent by 2015.

Noda, Japan’s sixth prime minister in six years, faces challenges even without Ozawa. He has an approval rating near 30 percent. If more lawmakers leave the DPJ, his party would squander its majority. Meanwhile, major opposition parties are threatening to submit a no-confidence vote against Noda this summer.

Yuki Oda contributed to this report.