In May 1933 he was appointed to be Undersecretary Minister of Interior, and forged an alliance with Galeazzo Ciano - opposing the Party bureaucracy, creating several secret services, and attempting to lessen the effects of Antisemitic legislation passed by the regime. Nevertheless, (and unlike Ciano), on 25 July 1943, Buffarini Guidi voted in favor of Benito Mussolini during Dino Grandi's attempt to have the latter deposed and get Italy to sign a peace with the Allies. As reward, after Nazi Germany intervened and rescued Mussolini in September, Guido Buffarini Guidi was appointed Minister of the Interior of the new Italian Social Republic (established by Nazis in Northern Italy).