The government has underestimated the strength of religion in the Soviet Union and should set the record straight, four prominent intellectuals said in a letter published Friday.

Publication of the letter in Pravda, the Communist Party newspaper, indicated at least some official support. It appeared on the day the Soviet Union ended its two-week celebration of the 1,000th anniversary of the arrival of Christianity in what is now the Soviet Union.Those signing the letter were sociologist Tatyana Zaslavskaya; literary critic and translator Sergei Averintsev; Ales Adamovich, a Byelorussian writer, and physicist Boris Raushenbach. All are strong supporters of Mikhail S. Gorbachev's effort to reform Soviet society.

"It is necessary once and for all to interpret the church in our country as a huge and complicated social phenomenon," they wrote.

The writers said religion must be an important part of Soviet life if the "customary dogma" of atheist propaganda cannot curtail the religious consciousness of millions of citizens.

"Figures on the number of believers, reported by regional and republican authorities in the Council on Religious Affairs of the USSR Council of Ministers patently, don't correspond to reality," the letter said.

A truer indication of its strength, the writers declared, is the 35 million rubles (56 million) the Russian Orthodox Church contributes each year to the Soviet Peace Fund, an official charity.

Western experts in the field believe there are tens of millions of religious people in the Soviet Union.

In their letter to Pravda, the four intellectuals proposed using the propaganda apparatus that preaches atheism to study "the real situation of religious consciousness of citizens of the USSR, to provide not illusory, but a reliable, scientifically based conception of this subject."

The constitution guarantees freedom of worship but it also guarantees freedom of anti-religious propaganda, which is carried out in schools, official publications and elsewhere.

A 1929 law on the relationship between state and church was adopted "in the period of huge social deformations," the letter said in an indirect criticism of dictator Josef Stalin, who was in power at the time.

Under that law, religious groups must register with the government and cannot do charitable work. It also restricts religious education.