Exodus of lawmakers from Japanese government undermines Prime Minister Noda By Yoko Wakatsuki, CNN July 2, 2012 -- Updated 0710 GMT (1510 HKT) The departing lawmakers are led by the influential Ichiro Ozawa They say they are protesting the prime minister's plan to double the sales tax It leaves the government with 249 out of 480 seats in the lower house Tokyo (CNN) -- More than 50 rebel lawmakers resigned from Japan's governing party on Monday, weakening the position of Prime Minister Yoshihiko Noda as he pushes a controversial increase in the sales tax through parliament. Led by the influential Ichiro Ozawa, 40 members of the lower house and 12 members of the upper house have left the Democratic Party of Japan, said Kenji Yamaoka, a senior lawmaker allied with Ozawa. They are leaving to protest Noda's plan to double the sales tax from 5% to 10% to try to tackle Japan's huge public debt, Yamaoka said. The lower house passed the measure last week despite opposition from the group led by Ozawa, a former party leader known for his political power-broking. The departures Monday whittle down Noda's majority in the lower house to an uncomfortable level, leaving the DPJ with 249 out of 480 seats. In the upper house, which is still to vote on the sales tax legislation, the party now holds 92 out of 242 seats. Noda, who took office in September, is the latest in a string of politically fragile Japanese leaders. He is the sixth prime minister in the six years since the departure of Junichiro Koizumi, who was in power for more than five years. The Ozawa-led exodus heightens the threat of a vote of no confidence being introduced against Noda. As things stand, his lower house majority should enable him to hold onto power. But any further departures would make him increasingly vulnerable. If he lost a vote of no confidence, he would have to either step down or call a snap election. Ozawa said last week that he expected that a general election could be called "in the near future."