WARSAW, OCT. 13 -- The banned Solidarity trade union will use part of a $1 million U.S. grant to purchase American-made ambulances and ship them to Poland to help hard-pressed provincial health services, union activists said.

A communique issued by a new working group today said Solidarity also would seek legal status for a "Solidarity social foundation" to establish specially equipped "diagnostic clinics" for workers in various parts of the country. The proposed clinics would be independent of the state-run health service.

The unusual initiative followed a decision by Solidarity's leadership to use the $1 million grant appropriated by the U.S. Congress last summer strictly for social programs rather than the union's organizing or underground publishing activity.

The appropriation, the first official U.S. aid to Solidarity, stirred controversy in Poland and caused unease among some of Solidarity's trade union backers in Western Europe.

The government of Gen. Wojciech Jaruzelski has made a major effort to use the U.S. donation in propaganda against Solidarity, labeling such union leaders as chairman Lech Walesa as "paid agents" and "clients" of the Reagan administration.

Union organizers said they hoped their use of the money would show Poles that Solidarity remained committed to the welfare of workers.

"Simple people should know that Solidarity as a trade union still cares about them," said Dr. Zofia Kuratowska, a well-known physician and member of the new Solidarity working group. "The ambulances will be evidence of the real intent of the union."

Kuratowska said the seven-member working group expected "to have many difficulties with the authorities" in carrying out its initiative and especially in obtaining court approval for legal registration of a foundation. She said, however, that she did not believe authorities would block donation of the ambulances to the state's own health services in poor areas.

"The government knows very well that the situation with the health service is very bad," Kuratowska said. "I can't imagine that someone at a high level would have such ill will as to refuse to accept our gift."

According to Kuratowska, Solidarity first will buy five or six ambulances, probably from Ford, for $45,000 to $60,000 each. The vehicles will have special equipment, unavailable in Polish ambulances, for emergency resuscitation and treatment of coronary patients.

The union also hopes to buy such equipment as ultra-sound units, mammography machines and sophisticated chemical testing materials for use in independent diagnostic centers that Solidarity would set up for use by workers. Tests would be free and would be used in part to identify medical hazards at workplaces.

Kuratowska said the union might seek the help of the Roman Catholic Church in finding sites and setting up the centers. She said Pope John Paul II expressed enthusiasm about Solidarity's overall plan for using the U.S. funds in a recent meeting with her.

All of the equipment would be purchased outside of Poland, meaning none of the American funds would be brought into the country, Kuratowska said. She added that a special committee of foreigners with links to Poland had been established to oversee the funds and their expenditure.

Within Poland, the working group established by Solidarity includes several well-known figures from the medical world such as Marek Edelman, a cardiologist and hero of the 1943 Warsaw ghetto uprising. Its unofficial coordinator is Krystyna Zachwatowicz-Wajdowa, a set designer and wife of director Andrzej Wajda, who promoted social programs by Solidarity during its legal existence.