In an unprecedented challenge to President Park Chung Hee's government, all opposition party members resigned from the National Assembly today to protest the expulsion earlied from the assembly of their party leader. t

The 66 members of the 230-member assembly submitted their resignations after a 45-minute debate to protest what they called the "shameful proceedings of the parliament" in ousting Kim Oung Sam on Oct. 4.

The progovernment parties expelled Kim that day for a series of critical comments directed at the government.

The resignations were an unprecedented display of unity by a faction-ridden party, part of which frequently supports the Park forces in the unicameral legislature.

Park's party can continue to operate the chamber with the help of a large bloc of members who are not elected but who are appointed with his advice.

But the resignations represent a blow to his prestige domestically. It appears to reflect a considerable grass-roots opposition to the expulsion the Park's party engineered nine days ago. Observers here said the mass resignations would not have occurred unless many members had been pressured by constituents angered by the expulsion.

A statement approved by the opposition members this morning declared, "We have resolved to resign in order not to be an accomplice of the illegal and irregular expulsion of our party president."

It accused the progrovernment Democratic Republican Party of "shameful proceedings" -- a reference to that party's use of armed guards to keep opponents out of the meeting at which Kim was expelled.

The two progovernment parties are expected to meet next week and reject the resignations in a peacemaking move designed to cool things off for the government.

However, it also is considered likely that the opposition members would continue to boycott the assembly at least for a considerable period of time.

The decision for a mass resignation had been reached at a party meeting yesterday at which 16 factional leaders had unanimously agreed to recommend the unusual step.

An outspoken critic of President Park, Kim was elected in May to head the New Democratic Party whose former leader, Lee Chul Seung, had frequently been accused of cooperating too closely with Park's Democratic Republican Party.

After a series of critical remarks about Park's dictatorial rule," Kim was expelled last week when Park's appointees and the ruling party gathered behing armed guards to vote him out.

Earlier, Kim had been stripped of his party post by a court that supported a suit against him charging that he had been illegally elected chairman in May. Kim called the ruling invalid and contended that it, too, was arranged by the government.

The New Democratic Party is usually split into two factions, one of which supports the government and rarely criticizes it except on some domestic issues.

Although it is generally powerless in the assembly because of the large number of presidentially appointed member, the party has shown consistent strength at the polls. In the last election in December it actually won a slightly higher percentage of the vote than Park's party did.

The 15 factional leaders' recommendation that all members resign will be presented to the entire party Saturday morning. If approved, as expected, the party will not participate in the assembly which reconvenes next Tuesday.

The government party had hoped that the opposition would not take so drastic a step. Technically, it can still vote to reject the resignations, a move which would permit some dissidents who want to return to the chamber to do so.

The government party chairman, Park Joon Kyu, said his party will meet Monday to decide whether to try to continue the work of the assembly without the opposition.

The resignation agreement today was reached with the concurrence of former party chairman Lee Chui Seung, who had counseled a cautious approach. The only dissent was made by a pro-government member who had been appointed caretaker chairman when the court ruled Kim's election invalid.