The debate on immigration legislation is heating up in a climate of fear engendered by economic malaise, concern over Haitian immigrants, anger at Fidel Castro for pushing 125,000 Cubans on the United States in 1980 and the repeated --but factually wrong--assertion that the United States is now accepting more immigrants than at any time in its history and more than the rest of the world put together.

Fear is a major factor behind an amendment introduced by Sen. Walter Huddleston (D-Ky.) that would lump refugees together with other immigrants under an overall world ceiling of 425,000 for all legal admissions to the United States.

The Select Commission on Immigration and Refugee Policy studied this and other immigration matters for two years. Finding that legally admitted immigrants and refugees contribute to the well-being of the United States in many ways (the creation of jobs, productivity, the strengthening of our Social Security base), it urged the Congress to distinguish between illegal and legal immigration and to differentiate further between lawfully admitted immigrants and refugees.

Should refugees be included in the cap? The answer of the 16-member bipartisan commission, which included eight members of Congress, was an emphatic and unanimous no. Rather, it endorsed the Refugee Act of 1980, which provides for a normal flow of 50,000 refugees annually and a process by which the president can increase that number in consultation with Congress.

The commission followed the principle of separating refugees from immigrants because to lump them together would be bad public policy.

First, it would compromise the United States morally, taking us back to the situation we faced in 1938, when we refused to admit orphan refugee children fleeing persecution and facing death because they came outside of the quotas set for immigrants.

Second, it is unwise to make refugees compete with close relatives of U.S. citizens and resident aliens for scarce visas. If it became important for the United States to rescue refugees in any given year, the immigration of relatives of U.S. citizens and resident aliens would be delayed, causing tremendous resentment.

Third, refugee policy is often related to foreign policy, and the president needs flexibility with respect to refugee policy that is not required concerning immigrants. A sudden flare-up in Poland, another rebellion in Hungary, or comparable developments elsewhere might require the president to act quickly.

Finally, it would not work for long. Precisely because of the pressures of foreign policy, Congress, under stimulation from the White House, would violate its own cap, as it did repeatedly through special legislation before the passage of the Refugee Act of 1980.

Advocates of the Huddleston amendment repeatedly exaggerate the number of illegal entrants to the United States, asserting, contrary to the careful work of the Select Commission, that 500,000 of them come into this country each year to stay. That number simply has no basis in fact.

The restrictionists also repeatedly use the number of persons admitted to this country in 1980 to support their charge that there are now more immigrants coming to the United States than ever before. That year was extraordinary because of the admission of 135,000 Cubans and Haitians as "special entrants" who were not admitted as immigrants under our normal, lawful admissions procedure and because we admitted the largest number of refugees in our history, 233,000, far above the average of 50,000 between 1960 and 1980. Nineteen-eighty was not the largest year of immigration in U.S. history. That was 1907, one of six years in which more than 1 million were lawfully admitted to the United States.

The severe restrictionists frequently assert that the United States accepts more immigrants and refugees than the rest of the world put together. Evidently, they do not count the refugees in Somalia or Pakistan. Tiny Somalia, with a miserable per capita gross national product of $130 has accepted more than 1.5 million refugees from Ethiopia--one for every 2.4 of its own population.

To permit the fear and confusion that underlies the Huddleston amendment to prevail in the Senate debate would constitute not just a concession to mean-spiritedness but also to irrationality.