Soviet Georgia's leading dissident was shown on national television last night delivering an abject confession that he had slandered the Soviet State.

Zviad Gamsakhurdia, heir to one of the most famous names in modern Georgia, was shown in a heavily spliced color videotape declaring: "I am guilty of . . . systematically preparing and distributing literature containing slanderous inventions defaming the Soviet state and social system."

Swallowing frequently though outwardly calm, the 39-year-old dissident asserted, "I sincerely regret what I have done and repent . . . and condemn the crime I committed. I want to note that after long reconsideration, I understood that I was deeply misled and that my activities were seriously harmful."

Then taped confession portions of which were shown on the leading Soviet evening news show, "Time", is a major prize for the Kremlin in its campaign to discredit the dissidents and human rights activists in the country.

The confession is sure to have substantial impact in Soviet Georgia, because of the man's name. He is the son of a major Georgian writer. Konstantin Gamsakhurdia, whose prose works in Georgian are widely known in the nationalist-minded trans Caucusus republic. The son's participation in the dissident movement there gave human rights activists a kind of instant recognition and prominence.

The confession included a reference to his father, who died several years ago. Zviad Gamsakhurdia said his father had "tried to cultivate in me love for and devotion to the Soviet people. I now profoundly regret that I did not heed my father's voice and embarked on the road of anti-Soviet activities."

Gamsakhurdia and another Georgian, Merab Kestava, also 39, went to trial in Tbilisi, the Georgian Capital, last Monday on charges of anti-Soviet agitation and propaganda. The same day, Juri Orlov, who founded a Moscow group to monitor Soviet compliance with internation human rights guarantees signed by the Kremlin, went on trial here, also charged with anti-Soviet agitation.

Gamsakhurdia was active in a group in Tbilisi that emulated Orlov's group. Orlov, who asserted his innocence throughout his trial, was found guilty and sentenced to the maximum penalty of seven years in prison followed by five years in Siberian exile. Gamsakhurdia and Kostava began their trial confessing guilt to the charge and received each received sentences of three years imprisonment and two of exile.

Despite the Georgians' pleas, the state put the trial on anyway, laying out its allegations of slaunderous activities aimed at undermining Soviet power.

Public confessions are unusual but not unprecedented here. In 1973, dissident Pyotr Yakir appeared at a press conference, condemning his own actions and those of other dissidents. Last year. Soviet television twice presented the confessions of foreigners seized when they were distributing human rights literature in the Soviet Union.

Andrei Sakharov, the human rights activist, told Western reporters when asked about the Gamsakhurdia confession, "I feel great disappointment. It is a heavy thing to see a man broken . It is hard for us to imagine the pressure and the isolution he faced, but the amazing thing is that people do stand up to such pressure, people like Orlov and Kostava. That Gamsakhurdia did not is his misfortune, his tragedy. his guilt."