Nearly 1,200 Poles associated with the banned Solidarity labor union have left their country for resettlement here under an unusual U.S. program, State Department officials said yesterday.

The resettlement program was started without announcement last July after months of public attacks by the United States and its allies on the Polish government's policy of pressuring Solidarity leaders to leave Poland.

The exodus of 300 to 400 activists, accompanied by families, is the product of parallel actions by the Polish government, the U.S. Embassy in Warsaw, the Geneva-based Intergovernmental Committee for Migration (ICM) and private sponsors here. All of the activists served time in prison or internment camps for political activity since the martial-law crackdown on Solidarity in December, 1981.

The emigrating Poles begin the first leg of their American journey with special "one-way passports" valid only for departure, and West German transit visas. Their first destination is a German resort hotel that has been taken over as a receiving station by the ICM, with U.S. financing.

According to a former regional leader of Solidarity who was resettled in Brooklyn last November, inmates in political detention camps were read Gen. Wojciech Jaruzelski's January, 1982, announcement that Solidarity activists could leave the country, and passport applications were subsequently distributed in the camps.

Some of those being held were permitted to leave the camps temporarily to travel to the U.S. Embassy in Warsaw and make their application for resettlement, according to the former activist, who asked that his name not be used.

The State Department insisted yesterday that "the United States has made no agreement with the Polish authorities," informal or otherwise, on the program to bring out the activists. However, Rep. Hamilton Fish Jr. (R-N.Y.), a member of the House Judiciary subcommittee on immigration, said his inquiries in Europe led him to believe that the arrangements were worked out with Polish authorities.

"They don't go around just handing out passports," said Fish, who said he had learned of the program by chance last January in a meeting with U.S. officials in Rome. Intrigued, Fish went on to the resort hotel at Bad Soden, West Germany, and came away impressed that this is "a limited program that is working extremely well."

After a television report on the program Tuesday on CBS News, an official of the ICM expressed concern that publicity about the arrangement might cause Polish authorities to have second thoughts. The official, who asked not to be quoted by name, said another 1,200 activists and family members are believed to be preparing in Poland for resettlement here.

State Department sources said the decision to undertake the program had been made last spring, when it appeared that freed Solidarity activists would be forced to return to internment camps if they did not leave the country. "It was a humanitarian necessity" despite everything that had been said in opposition to the Polish government's policy of pressure, one official said.

U.S. and allied embassies in Warsaw believe the activist emigration program is "winding down," according to State Department sources. The United States and its allies, some of which have taken smaller numbers of activists under programs of their own, are reported to be considering establishing a cutoff date for operation of the program.

About 10,000 Solidarity members are believed to have been incarcerated at one time or another following martial law. Only a minority has emigrated or applied for emigration at present, leaving Poland with a corps of activists that has diminished but by no means disappeared.