Prokhorov became a member of the Communist Party in 1950. In 1983, together with three other academicians – Andrey Tychonoff, Anatoly Dorodnitsyn and Georgy Skryabin – he signed the famous open letter called "when they lose honor and conscience" (Когда теряют честь и совесть), denouncing Andrey Sakharovs article in the Foreign Affairs'.