WASHINGTON, July 21--The House Committee on Unamerican Activities took to the warpath against Henry A. Wallace anew today after testimony that the Communists are "pushing" for a third party which he might head.

The testimony came from Walter S. Steele, chairman of the national security committee of the American Coalition of Patriotic, Civic and Fraternal Societies.

After hearing his story, the Committee asked for records he said he has on the ownership of the New Republic, weekly magazine of which Wallace is editor. Steele replied he would be glad to furnish them.

Steele, the first of 14 witnesses slated for a week of hearings on communist activities, testified that American reds have used wartime atomic experts on the faculties of their schools.

It was when he told of Communists working for a major third party of "leftists" that he turned to a discussion of Wallace, prompted by pointed questions from Rep. Mundt (R-SD).

The national committee of the Communist party issued a call at a meeting in New York City on February 23, 1946, Steele said, for "the immediate formation of a coalition of left wing elements into a third party" early in 1947.