In its first direct criticism of striking Polish workers, the Soviet Union tonight charged that "antisocialist forces" were trying to subvert Poland's socialist system.

The Charge by the official news agency Tass came after strike leaders Edward Gierek's concessions that included an offer of free and secret elections for trade unions that would be independent of Communist Party control.

Thus far, Tass had confined itself to carefully worded reporting of official Polish statements on the upheaval in that country and had accused unspecified Western circles of using the Polish developing to "blacken and discredit socialism."

Tonight, commenting directly on the crisis, Tass said: "Exploiting various subjective and objective difficulties that have arisen in the country, antisocialist elements are trying to join efforts in order to push Poland off the socialist road it has chosen, a road which meets the vital interests of the entire Polish people.

"The socialist system alone is the unshakable basis on which people's Poland can successfully advance in all fields," Tass said.

The comments were included in what Tass described as a roundup of news about the Polish situation. It was clear, however, that they were approved by top Kremlin officials since they represented a departure from the previously low-key reports on the delicate political dispute.

Moreover, Tass tonight spoke about "antisocialist elements" in Poland rather than unnamed imperialist forces outside that country as being responsible for the unrest.

Diplomatic sources here said that tonight's Tass statement was designed as a warning to the militant strike leaders who have so far resisted Gierek's attempts to appease them. In this view, such as warning may strengthen the position of Gierek's government, whose members have openly hinted that compromises were required to head off any direct Soviet Involvement.

[Soviet Communist Party leader Leonid Brezhnev left today on a scheduled trip to the provinces, Agence France-Presse reported. Observers said his departure appeared to indicate that the Soviets were planning no urgent action with regard to Poland.]

According to the diplomats, the main thrust of Gierek's effort at the moment is to induce workers to return to their jobs. Once this is done, the diplomats say, the movement for free trade unions is expected to lose much of its momentum, allowing Gierek to divide the leadership of the strikers.

[French President Valery Giscard d'Estaing today urged that Poland be allowed to settle its troubles by itself. The Associated Press reported that Giscard told his Cabinet that France considered Poland to have "fundamental importance for the equilibrium and peace of Europe" and hoped that Poland would "find in itself the means of overcoming its difficulties and responding to the aspirations of its people."]