In September 1950, the anti-communist magazine
Red Channels accused Bromberg of being a member of the American Communist Party. Subpoenaed to testify before the
House Committee on Un-American Activities in June 1951, Bromberg refused to answer any questions in accordance with his
Fifth Amendment rights. Bromberg refused to tell the Committee whether or not he was a member of the
Communist Party. He also declined to pledge his support in defense of the United States if ever there were a war with the
Soviet Union. Bromberg attacked the Committee for holding hearings "in the nature of witch hunts." As the result of his defiant testimony before the committee, Bromberg was
blacklisted from working in Hollywood. He suffered enormous stress from the ordeal; friends, such as
Lee Grant, noted that he aged considerably in a very short time. Bromberg and seven other Group Theater members were named by
Elia Kazan as Communist Party members in testimony before the House Un-American Activities Committee. According to Kazan in his 1988 autobiography
A Life, the Group Theatre Communist Party cell he belonged to in the Group Theatre met in Bromberg's dressing room. Members of the cell included
Clifford Odets and
Paula Strasberg. In 1951, Bromberg sought work in
England but died on December 6, during his fourth week of working in the
London play
The Biggest Thief in Town. He was 47.
Motion Picture Herald cited the cause of death as "natural causes." ==Broadway roles==