The Soviet Union tonight accused President Carter and his challenger Ronald Reagan of interfering in Poland's internal affairs.

The official news agency Tass, referring to the Labor Day speeches and other statements of the candidates in which they praised the accomplishments of Polish strikers, charged that the statements were part of Western efforts to advance a "so-called liberalization process" in Poland.

Tass also said that money was being collected in the West and sent to "those who virtually act to undermine" Polish socialism. United Auto Workers President Douglas Fraser said Sunday that American unions had sent about $120,000 to Poland to aid the families of strikers.

Tonight's comments on the Polish situation suggest that the Soviets are preparing a sustained publicity campaign to pressure the Polish leadership to hold the line and carefully backtrack on some of its pledges to the strikers.

In Washington, U.S. officials continued to take a low-key approach to the Soviet response to developments in Poland.

Tass said that "antisocialist forces" in Poland and abroad were using the current labor difficulties for "malicious" attacks on the Communist Party's "leading role in Poland, including that in the trade union movement." It cautined the Polish leadership that "complex decisions" must take "into consideration not only economic but also all other possible consequences."

Moscow television also criticized Carter's speech, saying he injected "his notorious notion of human rights" in the Polish developments. It ridiculed Reagan's remarks about the "American model" being favored by the Polish workers.

The broadcast also mentioned for the first time Lech Walesa, one of the leaders of the Gdansk strike, who was identified as "one of the members of an opposition group."

Carter and Reagan were accused of being part of an effort with an "obviously provocative purpose," to advance what Tass called "so-called liberalization."

"A definite meaning is being put into this notion: to take out class appraisals of the events taking place and to impose Western notions of 'freedom and rights,'" Tass said.

Many of the pledges made by Poland to the strikers contravene Marxist doctrine as interpreted by Moscow and some, such as those dealing with independent trade unions and the right to strike in a workers' state, are clearly heretical from Moscow's standpoint.

The charge of Western interference in this context, is presumably designed to construe Poland's labor unrest as part of a larger international conspiracy against socialism.

Tonight's comments amplified the basic criticism of the Polish developments outlined by the two authoritative newspapers, Pravda and Izvestia, yesterday. The expressed Kremlin opposition to the sweeping concessions granted to the workers by Polish Communist Party leader Edward Gierek and included warnings that the terms on some provisions will have to be narrowed.

Pravda today for the first time published news that an agreement "on a series of socioeconomic questions" had been reached in Poland and that workers have returned to their jobs.

Tass linked "antisocialist" forces in Poland, which it said are "putting forward demagogical slogans and demands," to unspecified Western visitors to Poland and to Western newsmen whose dispatches "are being readily used in the subversive activities against the socialist system in the country."