Business and farm leaders testifying before a Senate committee yesterday listed a litany of complaints about how import restrictions freeze America out of the Japanese market and asked the government to urge Tokyo to ease its restrictions before an undercurrent of anti-Japanese feeling intensifies in this country.

At the same time, business and labor combined to press a Senate subcommittee to oppose the Reagan administration's proposed 13 percent cut in funding for the Export-Import Bank, which lends money to foreign businesses and governments to purchase American-made goods.

The president of the Boeing Co., Malcolm T. Stamper, estimated his company lost $1 billion in airplane sales this year because of the restrictive policies of the Reagan administration and the Export-Import Bank.

The Boeing executive said his company's principal competitor, the Airbus, is challenging America's leadership in the world aircraft market because of the superior financing offered by the consortium of European governments that owns 70 percent of Airbus.

Similarly, Robert W. Galvin, chairman of Motorola, said Japanese limitations on imports of high technology from the United States cost American companies $15 billion in revenues in the late 1960s and early 1970s. The losses have continued, he said, amounting to $3 billion last year.

"Japanese protectionism in semiconductors has fundamentally altered the conditions of competition in the world for the foreseeable future -- to the disadvantage of American companies -- and the worse effects may be yet to come," Motorola's chief executive officer told the Senate Foreign Relations Committee.

He blamed "predatory pricing" by Japanese firms for undercutting American companies, including his own, in their home markets.

But Galvin, Robert B. Delano, president of the American Farm Bureau Federation, and James F. Bere, president of Borg-Warner Corp. and chairman of the Advisory Council on Japan-U.S. Trade Relations, said they did not favor a more protectionist U.S. policy to combat the Japanese. That, they said, could start a trade war that would harm both nations.

Nonetheless, they requested government help to force Japan to end its trade restrictions, especially on American farm products.

"We see Japan as exploiting its comparative advantage in industry and trade while thwarting other countries in their pursuit of similar interests in the agricultural area," Bere said.

Without mentioning Reagan administration attempts to thwart construction of a Soviet natural gas pipeline to Western Europe, Bere said he opposed the use of export controls as part of "sometimes unrealistic foreign policy objectives." He also expressed fears of a possible trade war if pending legislation passes that would require a proportion of all foreign cars to be made in the United States.

Committee Chairman Charles H. Percy (R-Ill.) warned that unless Japan opens its markets more to American products, especially farm goods, public opinion in this country would force trade restrictions on Japanese goods