A plebiscite called on two weeks' notice by Chilean President Augusto Pinochet to strengthen his hand against international human rights critics and internal opponents has instead caused a serious split inside the ruling military junta.

Gen. Gustavo Leigh, the air force member of the junta, declared in a letter to Pinochet - which is now making the rounds of Santiago - that Pinochet's announcement of the plebiscite was made over the opposition of two members of the four-man junta.

The letter is the first concrete evidence of the deep discrepancies long rumored to exist between Pinochet and Leigh over the President's inceasingly personalistic control of the military government.

Leigh's letter spelled out the air force's "rejection" of Pinochet's action in calling the referendum in a televised message as a violation of junta status. The navy junta member is known to hold a similar position.

Army Gen. Pinochet announced Dec. 21 an obligatory "national consultation" for next Wednesday in which all Chileans over 18 are required to vote yes or no to the proposition: "In the fact of the international aggression unleashed against the government of our country, I support President Pinochet in defense of the dignity of Chile, and reaffirm the legitimacy of the government to conduct with sovereign independence or institutionalization process."

The words "international aggression" refer to the fourth consecutive United Nations condemnation of the Chilean government for continued abuses of human rights.

For the first time, the General Assembly resolution passed early in December won the affirmative vote of the United States.

In the plebiscite, voters will be given a ballot on which in order to vote yes they must place a mark beneath a Chilean flag. They can vote no beneath a gray rectangle.

The officially dissolved leftist and centrist parties have rejected the referendum as a fraud and called on Chileans to abstain or vote no. But their statements have been banned as violations of the political "recess" in force under the 4-year-old state of siege.

A signed statement by three known members of the Christian Democratic Party advocating a no vote was printed yesterday in a Santiago newspaper. However, attempts by party members to distribute leaflets have been broken up by police or pro-government youths. A score of arrests have been made and today a policeman fired warning shots during an incident.

Pinochet was quoted yesterday as saying that those who oppose the referendum proposition "are the first traitors of Chile."

But the most serious objections to the holding of the plebiscite have come from within government supporters and the military - not that they agree with the U.N. resolution but that they think the planned plebiscite as constituted will further damage Chile abroad.

The result is a climate of escalating political tension reminiscent of the frenetic political struggles that were cut short by the rightist military coup in 1973.

In the week since the announcement:

Leigh's letter was leaked.

Pinochet's decree convoking the referendum was rejected as improper by the comptroller general, an independent career official empowered to rule on the legality of government actions.

The daily El Mercurio, a major pillar of junta support, suggested that in light of the comptroller's rejection, the plebiscite should be called off.

Conservative politician Jorge Rogers Sotmayor, author of the Chilean election law still theoretically in force, challenged whether a pebiscite could be organized according in such a short time and called for suspension.

Leigh argued in his letter that the "prestige" of the armed forces "would be compromised by the celebration of a plebiscite which would be controlled and judged by [the military] themselves."

There is no known effort to bring in observers who could assure that voting and counting is fair, even if the question posed were to be deemed fair.

The junta burned voter registration lists in 1974. Last July, Pinochet announced that elections could not be held until at least 1985.

Voters Wednesday must present their identity cards at any of several thousand poolling places, sign their names, and leave a thumbprint. Cards of those who do not vote will be rendered invalid, the government announced, and a blank ballot is to be considered in favor of Pinochet.

The fourth member of the junta is chief of the national police. His position is not known.