The recent flareup of dissent within the Soviet Union and Eastern Europe is bringing the Italian Communist Party under increasing pressure to better define its stand on civil liberties in this country and leading to growing criticism over its alleged failure to do so.

Although the Italian Communists have always been cautious in their relations with the Soviet Union, and in recent months have shown more restraint in their dealings with Eastern dissidents than the French Communist Party, the latest events have given the impression that the party is backtracking.

Western Europe's largest Communist Party, and its most powerful both in votes and in the sense that the party currently provides essential support ot the minority Christian Democratic government, the Italian Communists are widely considered the founders of Eurocommunism, a brand of communism that aims to combine socialism and democracy.

Because of their verbal commitment to Eurocommunism and their past outspokenness against the 1968 invasion of Czechoslovakia and for autonomy from the Soviet Union, expectations regarding the Italian Communists' support for Eastern Europe's dissidents have been high.

But after a brief flurry of pro-dissident statements in December and early January, the party appears to have had second thoughts.

As a party whose votes come mainly from Italians fed up with 30 years of Christian Democratic rule, the Communists' support for a Christian Democratic government has created confusion and some disaffection among its followers.

Despite a commitment to the Italian government's austerity plan, whose success theoretically hinges on the need to cut Italy's excessively high labor costs, the party has been unable to convince the powerful leftwing unions to give up an inflationary system of automatic cost-of-living wage increases.

Inside sources say party membership in the industrial north fell off by 10 per cent in the first weeks of the year. Most of the dropouts have been older workers schooled in the Stalinist period.A riot following an attempt last week by the party's top labor leader to convince striking Rome University students to return to their classes indicated the party's influence over Italian youth may also be waning.

So, it did not come as a surprise when, in a major speech to Communist workers in Milan at the end of January, party secretary Enrico Berlinguer downplayed dissent in the East, only briefly mentioning "certain illiberal characteristics of the political regimes of some countries of Eastern Europe."

Such criticism, he said, would not lead the Italian party to deny the "decisive historic function" of the 1917 October Revolution, the progress of the Communist countries and their "struggles for peace." Long excerpts from the speech were reprinted in the Soviet Communist Party daily pravda.

Berlinguer said last week on a nationally televised program that saw no reason for an ideological break with Moscow. He said he disagrees with Spanish Communist leader Santiago Carrillo that the Soviet Union is not a socialist country but a dictatorship of one stratum over the entire society.

Two weeks later in a front-page article in the independent Milan daily, Corriere Della Sera veteran Communist Giorgio Amendola warned Italians that, if they were looking for substantial changes in his party's nature, these were "vain expectations."

Communist leaders insist there has been no change in their basic position of independence from Moscow, commitment to Western democracy and acceptance of the NATO alliance. Last week, Berlinguer said he could not understand "why the judgment we Communists make of those Eastern societies should be tied ot our position in Italian society."

"Until recently the party appeared to be evolving in a direction we found quite encouraging," said a Western diplomat. But, he said, a growing trend toward a deeper analysis of the Soviet bloc society appears to have been ended by Berlinguer's Millan speech. It came a few days after another top Italian Communist, Giovanni Cervetti, met with Soviet ideologue Boris Ponomarev in Moscow.

"One might have thought that with a new administration in Washington and a new American ambassador on the way, the Communists might have used the present moment to send signals about their democratic intentions rather than for an about-face," he said.

[In Paris, French Communist Party leader Georges Marchais was asked at a news conference yesterday for his reaction to President Carter's letter of support to Soviet dissident Andrei Sakharov. "I am not going to take a position on Mr. Carter's action. But I can say that the American leaders are not the best placed to judge questions of freedom and democracy," he said, according to United Press International.]

Well-informed Italian observers said it was likely that the Communist's current internal weakness had convinced them that a return to their traditional ties might be advisable.

An unprecedented front-page article on dissent in Eastern Europe that appeared in the Communist daily Unita on Dec. 29 was followed by sharp criticism of the Czechoslovak government's treatment of the signers of the Charter 77 manifesto.

Italian Communists condemned the explusion of singer Wolf Bierman from East Germany. They deplored new arrests of Soviet dissidents. The Italian Communist publishing house decided to publish dissident Rou Madvedev's book "Was the October Revolution Inevitable?" Six top Italian party intellectuals signed a petition in favor of the Czecholovak dissidents that inside sources say had the leadership's tacit approval.

Then, there was a sudden uniting of the growing Italian Communist encouragement to the East European dissidents.

The party is clearly caught in a bind. Its traditional caution in public comments about the Kremlin reflects a desire to avoid alienating its own pro-Soviet elements. Some well-informed observers also suggest that pary leaders fear Moscow's ulimate weapon - stimulating a party split, definitively ending the Communists' dream of becoming Italy's No. 1 party.

"Our continued criticism of the Eastern regimes would have a major impact there, so we must be careful," one Communist senator confided.

For this season Italian Communist leaders claim their quiet and "soft" approach to the dissidence issue - so far Unita has not published any of the letters it has received from dissidents - os more effective than the "grandstand plays" of the French Communist Party, which has unequivocally criticized Soviet repression of civil liberties over the last year.