The Chilean government today outlawed the Christian Democratic Party, up to now the only non-clandestine party in overt opposition to Chile's military regime.

The decree signed by Chilean President, Gen. Augusto Pinochet and the three other members of the ruling military junta ordered the dissolution of all political parties in Chile under penalty of prison terms, banishment deportation and fines.

Although other parties were affected by the measure, it was directed at the Christian Democrats, whose newly elected president was accused last night of plotting to overthrow the government.

The decision marks a radical return to hard-line policies on political dissent in Chile after several months of relative tolerance and a lw level of repressive measures by the government. Earlier in the week the government added six more months to Chile's 42-month-old state of siege and its restrictions on civil rights.

Today's decree places the Christian Democrat Party in the same status as the Communist and other leftist parties that were outlawed after the Sept. 11, 1973 military coup. The Rightist National Party and Democratic Radical party and Social Democratic Leftist Radical party were decreed to be "in recess" after the coup and ceased political activity.

Only the Christian Democratic party, which introduced sweeping social and economic reforms during the administration of Chrisitan Democrat President Eduardo Frei from 1964 to 1970, continued to work politically and gradually increased its opposition to the authoritarian government despite the imposed recess.

The government charged last night that Party leader Andres Zaldivar and Tomas Reyes had been conspiring against the government and gave the press copies of papers printed by them that the government spokesman said contained a "subversive plan to bring about the fall of the government."

In another measure last night to tighten controls over potential dissent, the chief of the Santiago emergency zone, General Rolondo Garay, issued a military decree requiring prior authorization from his office for the publication of all news magazines and newspapers and "printed matter in general."

The former managing editor of the news weekly Ercilla, Emilio Filippi, a Christian Democrat, had announced plans last month to start a new news-weekly.