Pressman attended Harvard Law School with Alger Hiss, and served as editor of the Harvard Law Review, later joining (together with Hiss) the International Juridical Association (IJA), which "consistently followed the Communist Party line."
In 1933, Secretary of Agriculture Henry A. Wallace appointed Pressman assistant general counsel of the Agricultural Adjustment Administration; Pressman subsequently recruited Hiss and Nathan Witt into that office. AAA administrator George Peek resigned in protest, writing, that "in the legal division were formed the plans which eventually turned the AAA from a device to aid the farmers into a device to introduce the collectivist system of agriculture into this country."
Pressman would eventually testify that he had at the time been a member of the Ware group, an underground group of Communists in the Federal government. Pressman would also corroborate Whittaker Chambers' identification of Witt, John Abt and Charles Kramer as members of this Communist cell and admit under oath that he recognized Chambers.
Then he was general counsel in the Works Progress Administration from 1935, appointed by Harry L. Hopkins. Later in 1935 he was general counsel of the Resettlement Administration, appointed by Rexford G. Tugwell. After leaving government in June 1936 he became general counsel for the Committee for Industrial Organization (CIO) and for the Steel Workers' Organizing Committee. In March 1937 he became General Counsel for the Textile Workers' Organizing Committee.
In the 1930s Pressman was also a member of the Ware group, a group of American citizens employed in the United States government who considered Marxist ideologies a solution to the Great Depression, while secretly working for Soviet intelligence. As communists, Pressman and the members of the group were pledged to the violent overthrow of the United States government. In 1950 Pressman admitted to having been a secret member in 1934-35 and an ideological ally thereafter.
- Committee on Un-American Activities, House of Representatives, United States Congress, Hearings Regarding Communism in the United States Government—Part 2 (Washington: United States Government Printing Office, 1950), p. 2850 (PDF p. 16)
- Committee on Un-American Activities, House of Representatives, United States Congress, Espionage in the U.S. Government: Hearings under Public Law 601 (Washington: United States Government Printing Office, 1948), p. 643 (PDF p. 153)
- G. Edward White, Alger Hiss's Looking-glass Wars: The Covert Life of a Soviet Spy (Oxford University Press, 2004) ISBN 0195182553, p. 27
- "Report on the National Lawyers Guild, Legal Bulwark of the Communist Party," Committee on Un-American Activities, House of Representatives, United States Congress (1950), p. 12
- Allen Weinstein, Perjury: The Hiss-Chambers Case (New York: Alfred A. Knopf, 1978) ISBN 0394495462, p. 133
- George N. Peek with Samuel Crowther, “In and Out: the Experiences of the First AAA Administrator,” The Saturday Evening Post, May 16, 1936, p. 5
- HUAC 1950, pt. 2: 2850 [PDF 16]; cf. S. Rpt. 2050, 82d Cong., 2d sess., Serial 11574, Report of the Committee on the Judiciary Pursuant to S. Res. 366 (Washington: United States Government Printing Office, 1952), Appendix, p. 5503 (Exhibit No. 1402)
- Whittaker Chambers, Witness (Washington: Regnery, 1952) ISBN 0895267896, p. 612
- Gilbert J. Gall, Pursuing Justice: Lee Pressman, the New Deal, and the CIO (Albany, N.Y: SUNY Press, 1999), ISBN 079144103, p. 553
- Ralph de Toledano and Victor Lasky, Seeds of Treason, NY: Funk and Wagnalls, 1950, pg. 56 pdf.
- John Earl Haynes and Harvey Klehr, Venona: Decoding Soviet Espionage in America, Yale University Press