Prime Minister Masayoshi Ohira suffered a stunning defeat on a no-confidence vote in parliament today and was forced to dissolve the lower house call for new elections.

The victim of a long, bitter factional feud within the ruling Liberal Democratic Party, Ohira was deserted by about 70 members of the party. This enabled the opposition to achieve an easy 243-187 victory in the no-confidence vote.

It was the first time in 27 years that a Japanese prime minister has been beaten on a no-confidence motion.

Dissolution of the lower house of parliament means that for the first time in Japan's postwar history, elections for both chambers of the national legislature might be held at approximately the same time. The lower house balloting is expected to take place about June 20. Voting for the upper chamber had already been scheduled for June 29.

Ohira's humiliating defeat came unexpectedly on an almost routine motion to express a lack of confidence in his administration because of a financial scandal involving some officials and because of the nation's rate of inflation. s

Those issues were simply excuses seized on by the opposition parties to launch an attack on the prime minister.

Had all Liberal Democratic members stood behind their prime minister, the government would have survived by a narrow margin.

But Ohira was deserted by two old factional enemies, former prime ministers Takeo Fukuda and Takeo Miki, who refused to enter the parliamentary chamber and withheld their faction's votes. A last-minute effort to reach a compromise was in progress outside the chamber but it collapsed as the bell rang to signal the vote at hand.

Under the constitution, Ohira could either resign or dissolve the lower house and call for new elections. As Prime Minister Shigeru Yoshida did 27 years ago, Ohira chose not to resign.

The no-confidence vote came about 5 p.m. today, and the decision to dissolve the lower house emerged about three hours later from a special meeting of Ohira's Cabinet.

The factional feud that produced Ohira's debacle dates back many years and involves primarily his bitter struggles with Fukuda. Ohira is an ally of former prime minister Kakuei Tanaka, the disgraced party leader now on trial in the Lockheed bribery scandal, and he inherited Tanaka's longstanding fight with Fukuda.

Ohira ousted Fukuda from the premiership in a surprise victory December 1978, and their animosities never died out. Although complete details of today's party infighting have yet to be revealed, it appears that Fukuda saw a chance to embarass an old enemy and, as did Miki, told his supporters not to participate in the vote, thus ensuring Ohira's defeat.

The motion was filed by the Japan Socialist Party and supported by smaller opposition parties, including Komeito, the Japanese Communist Party, and the Democratic Socialist Party.

Socialist Party Chairman Ichiro Asukata contended that a no-confidence vote was necessary because Ohira's administration had become "untrustful" on issues involving political corruption.

That was a reference to Ohira's handling of a bizarre political scandal that is an offshoot of the Lockheed bribery case, which itself is still in the courts.

It was revealed early this year that a member of parliament named Koichi Hamada had lost an estimated $1.5 million in a Las Vegas nightclub gambling hall. Public prosecutors suggested that some of the illicit Lockheed money may have been used to pay Hamada's debts. The name of Kenji Osano, a defendant in the Lockheed case and friend of Tanaka, emerged as the possible source of money used to bail Hamada out of his troubles.

Hamada resigned from parliament but opposition party members demanded that he appear before a committee to testify on the gambling debt. Ohira opposed forcing his testimony, protecting Tanaka and his friends.

The opposition had tried to make a major issue of the Hamada case and Ohira's role in it but it had never reached proportions of a major political scandal.

Asukata also raised the inflation issue against the prime minister, although Japan's rate is one of the lowest in the industrialized world -- an estimated 6.4 percent this year.

Asukata charged that the government's consumer price statistics were "lies" and claimed that with recent increases in gas and electric prices, the real inflation rate is much higher.