The Soviet Union condemned the congress of Poland's independent trade union federation Solidarity tonight as an "antisocialist and anti-Soviet orgy" that has adopted the course of "open struggle" against Polish communist authorities and against the socialist system in all Soviet Bloc countries.

The official news agency Tass, in a commentary evidently approved by the highest Kremlin authorities, warned of a "mounting wave of indignation" at actions taken by the Gdansk congress of Solidarity. It said Warsaw and Moscow "are linked by the bonds of fraternity, common interests, and common socialist aims" that cannot be broken.

Communist observers here said this was the sharpest attack on the union since the outbreak of the Polish crisis a year ago and that it may foreshadow a showdown in Poland.

According to these sources, the statement suggested an assessment here that the crisis has reached a point where the Polish government will have to move decisively against the union or by its inaction invite outside intervention.

The 1,000-word commentary was read in full over Moscow television tonight after a broadcast of extensive footage of Soviet military maneuvers in Byelorussia, the three Baltic republics and the Baltic Sea.

According to Scandinavian intelligence reports, a Soviet armada of 60-80 ships -- one of the largest such fleets seen in the Baltic since World War II -- moved south along the Soviet coastline Thursday as part of the exercises, The Associated Press reported.

Political observers here said the harsh tone of the Tass commentary and its wholesale condemnation of the congress suggest that the Soviets apparently have given up all hope that a compromise solution with Solidarity was possible.

In contrast to previous public attacks on Solidarity that sought to differentiate between various factions by reserving the sharpest condemnation for "extremist leaders" in the union leadership, tonight's commentary castigates all "union chiefs" and made one reference to "Solidarity's extremist leaders."

"The congress of Solidarity at Gdansk is, as its participants declared, a review of the forces that are getting ready for a struggle for power," Tass said.

Tass said that "the speeches and documents passed by the congress leave no doubt about the real aims of the sponsors and inspirers of the Gdansk assemblage. The congress has as a matter of fact grown into open struggle against the Polish Communist Party and the Polish government. It has been declared that the course of this struggle for power in the country, Solidarity intends to use all available means."

The agency then added a more ominous comment about the threat to socialism in the entire bloc.

"The so-called appeal to the peoples of Eastern Europe, which contains a call for struggle against the socialist system, is openly provocative and impudent toward the socialist countries."

The comment came a day after a Solidarity resolution expressed support for workers in other East European countries who would seek to organize in independent unions. East Germany and Czechoslovakia particularly are concerned that the course of events in Poland could affect adversely communist authority in their own countries.

Tass said Solidarity "and all those to whom the framework and scale of the struggle against socialism on Polish soil already seem narrow have launched . . . interference in the affairs of other peoples."

Tass said those gathered at the "so-called trade union congress" "hate socialism and the people's power in Poland and are guiding things toward undermining the foundations of the Polish socialist state, violation of international alliances of the Polish People's Republic and the restoration in the long run of the bourgeois system in Poland."

The congress, Tass said, "exposed the real face of Solidarity's extremist leaders and the circles in Poland and outside it that are responsible for the crisis and anarchy in the country and that are whipping them up in every possible way."