The confession to anti-Soviet wrongdoing by jailed dissident Russian Orthodox priest Fr. Dmitri Dudko, 58, that was unveiled last night is one of the heaviest blows to be struck in recent years by the KGB secret police against the struggling Soviet human rights movement.

Dudko occupied a unique and important place in the spectrum of influential dissidents who have risked jail to speak out for inividual freedoms within this authoritarian system. His plainspoken sermons and tracts appealed to many countrymen who would like to practice their religion openly but fear to do so.

His views have been circulated widely in the West, especially in Western Europe, and dozens of eminent religious figures and humanitarian organizations had joined in calling on the Soviets to free him after he was jailed Jan. 15.

The confession, televised nationally here, comes after six months behind bars and secret interrogation. But unlike the wooden and forced performances given by other dissidents who have recanted in recent years, Dudko looked and sounded both eager and intent upon recanting his crimes.

"I have seen that I yielded to the propaganda voices which are directed at undermining our system and I failed to see what is really being done in our country for the benefit of the people . . . I repudiate what I have done and assess my so-called struggle against the Soviet power."

The formulation may not sound spontaneous, but the delivery was smooth and even convincing. ""A real performance that hurts every part of the movement," one dissident commented.

The priest, who had been in Stalinist labor camps for eight years, in 1973 organized question and answer sessions with parishioners at his church here, the Cathedral of St. Nikolai. Those who were there at the time remember these sessions still as remarkable moments of frankness in a society deadened by lifeless official diction.

In mid-1974, church authorities barred Dudko from such discussions and later transferred him to a provincial parish. Last fall, Dudko was imprisoned.

Dudko's wife, Nina, said today her husband has been released from jail, but the charges are still pending against him. She refused to let correspondents speak with him.