He came to oppose Joseph Stalin and rallied with the Left Opposition, being marginalized inside the government and sent as Soviet ambassador to London and Paris, where he was involved in renegotiating financial settlements. He was ultimately recalled from France in autumn 1927, after signing his name to a controversial Trotskyist platform which endorsed world revolution. Credited with having developed the Trotskyist critique of Stalinism as "bureaucratic centrism", Rakovsky was subject to internal exile. Submitting to Stalin's leadership in 1934 and being briefly reinstated, he was nonetheless implicated in the Trial of the Twenty One (part of the Moscow Trials), imprisoned, and executed by the NKVD during World War II. He was rehabilitated in 1988, during the Soviet "Glasnost" period.