Soviet Baptist pastor Georgi Vins has told a congressional committee here that religious persecution in the Soviet Union is on the increase rather than diminishing, as some have contended.

"Georgi Vins has been released, but many thousands of evangelical Christians and Baptists and other believers in the U.S.S.R. are being persecuted for the Christian faith even today'" said the dissident religious leader. In April, Vins and four other Soviet prisoners were brought to this country in exchange for two Soviet spies.

Vins testified here last week before the Commission on Security and Co-operation in Europe, an independent panel of members of Congress and representative of the executive branch concerned with implementation of the 1975 Helsinki accords.

Speaking through an interpreter, Vins charged that the KGB (the Soviet secret police) is spying on believers in their homes and churches, using American-made bugging equipment. "The KGB bought it in the fight against believers," he charged.

For the 50 million evangelical Christians in this country, and particularly for Southern Baptists, Vins has become the symbol of Christian resistance to the official atheism of the Communist government.

He is secretary of a group of Baptists called the Council of Churches. It is commonly referred to in this country as the Reform Baptists. This group broke from the All-Union Council of Evangelical Christians and Baptists - the church officially recognized by the Soviet government - and has been denied government recognition. In the eyes of the government, it exists illegally.

"The Council of Churches is compelled to carry out all its organizational work under conditions of secrecy," Vins said of his church. But he added: "At the same time a large part of its spiritual work, prayer meetings and worship meetings in churches, baptism of believers and crowded meetings on festival days, are conducted openly, despite attacks by the militia and the KGB."

At the present time, Vins said, only about 40 leaders of his group, including the chairman, Gennadi Konstantinovich Kryuchkov, are in prison. There would be far more imprisoned, he told the commission, "were it not for the mercy of God and prayer support and petitions on the part of Christians throughout the world."

Vins imprisonment has been the focus of concern by evangelical groups in this country in recent years.The pastor said that the voices raised here in his behalf had a moderating effect on the treatment he was given.

Vins said that he suffered a double hernia from the heavy labor he was forced to do during his first term in prison camp. Between that and a poor diet, he said, "in a few months my health was ruined."

But after the Congress adopted a resolution in 1976 expressing concern over Vins' imprisonment "my living conditions began to improve radically," he said. "I was in the hospital for a year under the care of doctors and got a special hospital diet. I attribute that directly to the concern which you all have raised here in my behalf."

Vins, who has spent eight of the last 13 years in prison, said in response to a question that he was convicted "for publishing a religious journal; for maintaining contact with a Christian printing press;" for making public the account of a young soldier in the Soviet army "who in 1972 was tortured to death in the Crimea" and for "organizing a Sunday school for the religious education of children."

He declared that "my actions and those of my fellow pastors were not crimes. We merely want to have the opportunity to preach the Gospel to the Russian people."

Vins, whose wife and five children are scheduled to join him in this country, said when he was imprisoned, "the authorities sent me 6,000 miles away from the Ukraine where his family lived "to make it difficult for my family to come to see me."

"When my family did come to see me they [prison authorities] gave us only a day together . . . The KGB put microphones everywhere and recorded all the most intimate discussions," he said.

While praising the devotion and fidelity of evangelical and Pentecoastal Christians in the Soviet Union, Vins had only scorn for his fellow Baptists within the officially recognized body, the All-Union Council.

He described the leadership of the group as "a body linked in the closest possibe way with the state authorities, including the KGB."

Representatives of the All-Union Council, he said, "travel widely throughout the whole world proclaiming the imaginary religious freedom in the USSR."

Vins' Baptist group, called the Council of the Churches, split from the larger Baptist body in 1965 over the question of acquiescing to strict governmental restrictions on religious activity. CAPTION: Picture, GEORGI VINS . . . KGB fights "aginst believers"