The party helped Mossadegh establish the National Front, nationalize the oil industry and rise to power. Some members held office during Mosaddegh government. It was suppressed following the British–American backed coup d'état in 1953 and was outlawed in 1957, on the grounds that it had an alliance with the Tudeh Party of Iran ten years earlier. It was revived in 1960 and actively contributed to the National Front (II), which was disintegrated in 1963 and forced to survive secretly. Iran Party held a congress in 1964. Not much is known about the activities of the party between 1964 and the mid-1970s except of some irregular meetings and exchanging views. In 1977, alongside League of Socialists and Nation Party it revived the National Front (IV) and demanded Ruhollah Khomeini's return to Iran. In early 1979, then secretary-general of the party, Shapour Bakhtiar was appointed as the last Prime Minister by the Shah and included two Iran Party members in his cabinet. The party however denounced his acceptance of the post, expelled him and called him a "traitor". The party did not play an important role in Iranian political arena after 1979 and was soon declared banned.