Relatives of three imprisoned dissident figures whose trials last summer attracted world-wide attention today accused Soviet authorities of cutting off communications with the men as part of a continuing harassment campaign.

The charge by the relatives that the authorities were violating Soviet regulations providing for periodic communications of prisoners with their families could again focus Western attention on these human rights activists.

The trials of Anatoli Scharansky, Yuri Orlov and Alexander Ginzburg produced an uproar in Washington last summer, bringing U.S.-Soviet relations to the lowest point during the Carter administration.

The continued harassment of humand rights activists -- who were convicted of anti-Soviet activities or espionage in Scharansky's case -- may well be used by opponents of a new Soviet-American strategic arms limitation when the issue is debated in the Senate.

Orlov, sentenced to seven years' labor camp imprisonment and five years' internal exile, was said today to be in "unstable health" by his wife. Friends said his illness meant he could not fulfill his camp production quota and had been officially reprimanded as a result. Each reprimand causes further loss of already sharply limited privileges.

The wives of both Orlov and Ginzburg said they had not received letters as expected in January and which the men have the right to send.

Scharansky's mother, Ida Milgrom, said her correspondence with her son also has been interrupted. She said there have been illegal delays in providing her with the court decree and sentence handed down against her son last July. This in turn has prevented her from attempting an appeal of the verdict. Scharansky was convicted of treason by espionage and sentenced to 13 years' imprisonment.

Orlov and Ginzburg were confounders of a Moscow group that seeks to monitor Soviet compliance with the human rightls provisions of the 1975 Helsinki accord on European security and cooperation.

In other disclosures at a press conference today, it was said that more than 700 persons and families had been helped in the past year by the relief fund for political prisoners and their families established by exiled Nobel Prize laureate Alexander Solzhenitsyn.

It was said that among the recipients were about one hundred Soviet citizens incarcerated for political reasons in psychiatric hospitals; 100 others who needed money to travel to see relatives imprisoned or exiled in remote parts of the country; and about 25 persons who needed money to help pay lawyers' fees to defend themselves against political charges.

Irina Ginzburg said contributions to the fund "from ordinary Soviet citizens" have increased in recent months, and totaled about 2,000 rubles ($3000) for the month of January. Most of the money comes from royalties earned by Solzhenitsyn's epic of the Stalinist prison camp system, "Gulag Archipelago."