Beginning in 1950, after eight years of professional writing, Lampell could not get work. The reality of the Hollywood Blacklist soon became clear: Lampell was suspected of Communist political associations and was being shut out of work in the entertainment industry as a result. With no legal charges, no formal accusations, or any explanation of the situation, there were no means for Lampell to defend himself or even inquire about his status.
Lampell’s name was included in Red Channels: The Report of Communist Influence in Radio and Television, the pamphlet published by former FBI agents in 1950 of individuals in the entertainment industry who they accused of Communist affiliations. Simply having his name in this publication was enough to keep producers away from Lampell: while there was no single definitive source on which the industry-wide shut-out was based, the list in Red Channels was as close as there was to an actual blacklist. Lampell felt the immediate effect of his inclusion on the list, as his income slowed to a trickle. Documents from the collection suggest that these accusations were based on his time with the Almanac Singers and their involvement with Leftist organizations, labor unions, and causes shared by the Communist Party of America.
Lampell was called to testify before Sen. Pat McCarran’s Senate Internal Security Subcommittee in 1952. Lampell was accused of taking part in a subversive Communist conspiracy, with his presence at various Left-wing benefits and functions as evidence. Asked to testify if he was a Communist and to “name names” of Communists in the entertainment industry, Lampell invoked the Fifth Amendment. Lampell felt it was not only his right but a moral obligation to resist invasions into his private beliefs. He also refused to "clear" himself of the accusations in public, even though it would have ensured a return to work, as he felt it was wrong to set a standard to which others in his position would have to meet to return to work and did not want to contribute to the conditions of the Blacklist.