The gap between rich and poor in the Soviet Union is widening dramatically, a major survey of life there indicates.

Also, Soviet citizens are turning with increasing eagerness to forbidden private enterprise to get ahead in an economy that they perceive as flagging. The survey indicates that those not engaging in illegal private work -- because of conscience or lack of skills -- may find themselves impoverished.

Ironically, the communist superpower must rely increasingly on home-grown forms of private enterprise, the survey shows. In addition, the widening gap between economic groups contradicts the official portrait of the Soviet Union as a place of increasing economic homogeneity.

These are among the preliminary findings emerging from the most comprehensive probe in 30 years into the lives and attitudes of Soviet citizens.

The Soviet Interview Project (SIP), a five-year, $7.5 million U.S.-financed effort, surveyed 2,800 Soviets who recently emigrated to the United States.

The results are being analyzed by specialists in sociology, politics, economics, nationalities and other fields. Their leader is James R. Millar, director of international programs and an economics professor at the University of Illinois in Champaign, project headquarters.

The Soviets were drawn from thousands who emigrated between 1979 and 1981. They were virtually the last of an unprecedented wave of more than 250,000 Soviet citizens, most of them Jews, for whom the bar to emigration was lifted as part of the detente policies of the late Leonid I. Brezhnev. After the Soviet invasion of Afghanistan five years ago, the Kremlin reduced emigration to a trickle.

The SIP survey concentrated on how the Soviet system works, how Soviet citizens make the system work for them and where Soviet citizens think the centrally run economy and society is headed.

The last such survey was the Harvard Project of the 1950s, which questioned thousands of post-World War II Soviet emigrants.

Preliminary findings seem likely to stir debate among Soviet specialists here and abroad about life and attitudes among the Soviet Union's 272 million citizens.

Several findings indicate citizens' deepening disaffection with the Kremlin. For instance, analyst William Zimmerman of the University of Michigan found a marked increase in draft evasion, the use of bribery and influence-peddling to obtain first jobs and university positions, and refusal to vote in the nation's single-candidate elections.

Part of this increasing independence can be traced to the gradual dimming of the years of terror during the dictatorship of Joseph Stalin, who died in March 1953. But part seems to be due to what some researchers call the rising "privatization" of attitudes and life styles.

"Thought crime" and other kinds of nonconforming behavior apparently are rising, according to John Garrard of the University of Arizona and the Kennan Institute for Advanced Russian Studies in Washington. Garrard found that Soviets between ages 20 and 40 were most likely to do such officially unacceptable things as listen to foreign radio broadcasts, read underground literature, hold religious beliefs or attend unofficial art exhibitions.

"There is a lot of 'thought crime' in the Soviet Union today, but overt behavior is a very, very small proportion," according to Garrard.

Among the principal findings were Aaron Vinokur's on wealth and poverty. Vinokur, a Soviet economist living and teaching in Haifa, found that by the end of the 1970s, 44 percent of the wealth in the Soviet Union was in the hands of 10 percent of the population. "There was an increase in economic inequality, as family income, savings and wealth were increasingly unequally distributed," he said.

Vinokur found that the wealthiest citizens supplemented their state-set salaries with income from private work. They include doctors and dentists with private practices, college-level teachers who also tutor and drivers who take money for private trips.

Those whose incomes were lagging, he found, were semi-skilled factory hands, waitresses, saleswomen and other women in the service industries.

Vinokur found that the top 5 percent of Soviet families had an average monthly income of 1,212.7 rubles ($994.41) compared with 149.6 rubles ($122.67) for the bottom 5 percent.

"The meaning is that the lowest 5 and 10 percent of the population is below the poverty line," Vinokur said.

"The Soviet Union is very tolerant of private jobs, not of speculation, such as black-market activities or dealing in foreign currency," Vinokur said. "The regime today differentiates between private jobs and economic crimes."

About 85 percent of those interviewed were Jews. Most of them were from cities.