The La Follette Civil Liberties Committee, or more formally, Committee on Education and Labor, Subcommittee Investigating Violations of Free Speech and the Rights of Labor (1936-1941), began as an inquiry into a National Labor Relations Board (NLRB) investigation of methods used by employers in certain industries to avoid collective bargaining with unions.
Between 1936 and 1941, the subcommittee published exhaustive hearings and reports on the use of industrial espionage, private police agencies, strikebreaking services, munitions in industrial warfare, and employers' associations to break strikes and to disrupt legal union activities in other ways. Robert M. La Follette, Jr., a Republican and Progressive Party Senator from Wisconsin, chaired the Committee.
The Committee investigated the five largest detective agencies: the Pinkerton National Detective Agency, the William J. Burns International Detective Agency, the National Corporation Service, the Railway Audit and Inspection Company, and the Corporations Auxiliary Company. Most of the agencies subpoenaed, including the Pinkerton Agency, attempted to destroy their records before receiving the subpoenas, but enough evidence remained to "piece together a picture of intrigue". It was revealed that Pinkerton had operatives "in practically every union in the country". Of 1,228 operatives, there were five in the United Mine Workers, nine in the United Rubber Workers, seventeen in the United Textile Workers, and fifty-five in the United Auto Workers that had organized General Motors.
The Committee reported that as late as 1937, its census of working labor spies from 1933 to 1937 totaled 3,871 for the period. Private security firms like the Pinkerton National Detective Agency and Burns were employed to infiltrate labor unions. The Committee concluded that espionage was "the most efficient method known to management to prevent unions from forming, to weaken them if they secure a foothold, and to wreck them when they try their strength."