Prime Minister Surya Bahadur Thapa, the first prime minister elected under Nepal's partyless parliamentary system, resigned today following a crushing defeat in a no-confidence vote in the National Assembly and in the wake of the resignations of most of his cabinet.

Amid charges of widespread official corruption and government ineptitude, Thapa was defeated in an opposition no-confidence motion by a vote of 108 to 17, with 11 abstentions. Five hours later, the government was dissolved and an election for a new prime minister was scheduled for Tuesday.

The collapse of the government came after 22 members of Thapa's 35-member Council of Ministers, including his closest allies, resigned to protest his economic policies and alleged malfeasance in government.

The rebellion and forced resignation represented a major victory for advocates of a liberalization of politics under Nepal's constitutional monarchy, and appeared to reflect an attempt by King Birendra to broaden the democratic process in Nepal and allow the National Assembly to develop a greater sense of responsibility.

Opposition leaders noted that although the king could have put down the cabinet rebellion any time after ministers began resigning on June 24, he permitted the National Assembly to make Thapa 55, the first prime minister to be forced out of office by the parliamentary process.

The most likely successor appeared to be Lokendra B. Chand, a 49-year-old former speaker of parliament and one of the key sponsors of the no-confidence motion.

A possible challenger to Chand in Tuesday's election is the speaker of the assembly, Marich Man Singh, who is regarded as more conservative.

Political observers here said the outcome of a Chand-Singh contest would determine whether the assembly assumes greater powers in Nepal's political system, although they said the king and his palace counselors will likely continue as the real power center.