TOKYO, DEC. 8 -- Members of Japan's reform-minded opposition today elected former prime minister Toshiki Kaifu the first chairman of their new coalition party, the New Frontier Party.

The new party, which will be inaugurated formally on Saturday, is a collective endeavor formed by members of several parties and factions. With about 185 members in the lower house of parliament, it will be the second-largest party in Japan.

Kaifu's chief job will be to take his new party into a general election and try to win power back from the current government, an ad hoc coalition formed five months ago and headed by Socialist Party Chairman Tomiichi Murayama. But Kaifu could not say today when an election might be held.

The New Frontier's chief architect and strategist, Ichiro Ozawa, was elected to the party's number two job, secretary general.

The big new opposition party is second in size only to the Liberal Democratic Party -- despite the name, the most conservative of Japan's major parties -- which is the biggest party in Murayama's governing coalition.

Many New Frontier members are former Liberal Democratic politicians; Kaifu was the party's president and prime minister from 1990 to 1992. Kaifu is closely associated in the public mind with the fight against political corruption; he was cashiered by leaders of the Liberal Democrats in 1992 because they feared he was pushing too hard to pass an anti-corruption bill.

Kaifu defeated former prime minister Tsutomu Hata and Democratic Socialist Party Chairman Takashi Yonezawa for the party chairmanship.

The most interesting thing about the New Frontier Party's election for party chairman is that an election was held at all. Normally, a new party would be expected to choose a leader through Japanese-style consensus building, with a long series of closed-door meetings at which everyone would informally agree on a single person.