Three years after the specter of starving refugees brought an international outcry and a flood of relief aid, Cambodia has become caught in the middle of a dispute among United Nations agencies and western donor countries over whether to continue food assistance to the Vietnamese-installed government in Phnom Penh.

With about $714 million already spent in one of the costliest relief programs in U.N. history and food production vastly increased, virtually everyone involved agrees that the emergency in Cambodia is over.

The dispute thus concerns whether the situation remains so delicate and the risk of deterioration so great as to warrant additional food aid to the Cambodian interior in 1983.

It revolves around a report by a four-member "assessment mission" of the U.N. Food and Agriculture Organization and presented to a meeting of western donor nations in New York Dec. 15.

The donors agreed to continue aid to refugees on the Thai-Cambodian border but deferred a decision on assistance to the interior until Jan. 25.

Also at stake is the presence in Phnom Penh of the FAO and the World Food Program, the U.N. agency with the largest operations in Cambodia.

Proponents of continued U.N. food aid to Phnom Penh--chief among them the FAO--argue that an expected rice shortage of 100,000 tons in 1983 and malnutrition among children justify the additional assistance.

Opponents, including the United States and most other western donors, question these findings and say it is time to end the program. Some relief officials also assert that FAO and other U.N. officials favoring continuation are engaged in empire-building and have vested interests in their Cambodian operations.

Both sides appear motivated in large measure by politics, splitting along lines of support or opposition to the pro-Moscow communist government installed in Phnom Penh by invading Vietnamese forces in January 1979.

Critics of continued aid also charge that corruption among Phnom Penh authorities, diversion of supplies to Vietnamese troops and the government's failure to distribute its resources properly have limited the effectiveness of the aid program. In addition, they say, the Soviet Bloc has effectively shunted responsibility for food aid to the western donors and did not deliver any such aid in 1982. According to relief officials, the Soviets explained this by saying they had made credits available and the Phnom Penh government had not asked for any food assistance.

In 1981 the Soviets originally pledged 100,000 tons of food aid but delivered only about 45,000 tons, relief officials said. Apparently embarrassed by disclosure of the shortage, the Soviets in 1982 did not reveal the amount of their aid, consisting of some equipment and supplies for food production, the officials said.

U.N. aid provided by the western donor nations "is considered complementary to bilateral aid" from the Soviet Union and its allies, one western relief official said, "but in fact the U.N. aid has been the biggest block of civilian aid to Cambodia."

The FAO estimates the 1983 rice deficit will be 100,000 tons.

The report recommended emergency food aid deliveries of about 32,000 tons of rice for deficit areas and immediate special feeding programs for children. It added that "the continued presence of FAO in Phnom Penh would seem desirable, as the country needs further international help in the food and agriculture sector to reduce the risk of deterioration in the supply situation."

A senior U.N. official in Bangkok, acknowledging donor opposition to continued aid, said, "There will be a reduction for the interior. How much is anybody's guess. It may be zero." In 1982 the western donors provided about $34 million worth of aid, including 50,000 tons of food, he said. Of the $714 million aid total since October 1979, about $368 million has gone to the Vietnamese-controlled interior.

"If there is to be assistance in 1983, it will have to be on the basis of clearly specified deficit areas," the official said. "We would want assurances we would be able to monitor implementation and report on the outcome." He said there would be no more "dumping food" on the Phnom Penh authorities to distribute as they wish. "The emergency's over as far as that's concerned."

A western relief official familiar with the aid program in Phnom Penh said that "1982 has been a very bad year for monitoring." He cited "a drastic decline in the number of field trips" that the authorities have permitted relief officials.

"Corruption in Cambodia has grown tremendously," he added, and large amounts of U.N. food aid never reach the intended recipients. "The bulk of the food is distributed among government officials," he said.

He added that according to Phnom Penh government reports, a third of the food aid is distributed in the capital, where about 10 percent of the population live. Much of it is resold, the official said, and some of it squandered. He recalled that two government officials had casually mentioned to him that they were using U.N. rice to feed their chickens and pigs.

There also have been reports of diversion of U.N. food aid to Vietnamese forces occupying the country. Vietnamese defectors who have fled into Thailand have reported receiving U.N.-supplied goods to supplement their rations.

In September 1981 several U.N. officials visiting Cambodia's main port of Kompong Som saw Vietnamese soldiers loading tons of U.N. rice from a Singaporean freighter directly into Vietnamese military trucks.

Besides charging that some of the U.N. aid is used improperly, opponents of continued assistance question the FAO's estimate of a 100,000-ton rice shortage on grounds it is based on a high population estimate of 7 million derived from Cambodian government figures. Some East European embassies in Phnom Penh reportedly estimate a population of about 5 million.

In addition, skeptics note that Cambodia has a number of food-surplus areas and assert that the government is not doing enough to distribute supplies evenly.

"U.N. agencies can't act as a substitute government," a western relief official said. "Food should not be shipped in to relieve the government of the task of governing and redisibuting its resources."