Paolo Ferrero from Italy's Communist Refoundation Party said that Matteo Salvini was "not a jackal but a Nazi," in March last year.
The comments were made in a Facebook post, which continued: "Salvini uses the disasters and the disorientation created by neoliberalism to artificially construct a war between the poor, while making scapegoats out of what is different," he continued in his post.
However, Salvini's legal complaint about the remarks has been thrown out by a Turin judge.
"In the environment of political criticism, verbal constraint takes on a peculiar elasticity due to the often heated and severe tone which characterizes political battles," the judge explained in his closing statement.
In his opinion, he continued, Ferrero's accusation of Nazism "seems to refer not to the criminal policies of xenophobia and genocide, but rather to the early policies of the movement, aimed at constructing false enemies to create social hatred."
Ferrero celebrated the acquittal by repeating his comparison between Salvini and Hitler's party.
"There are evident parallels between the words and concepts used by Salvini and those used by the Nazis," he said, according to La Repubblica.
"Calling things by their proper name is the first step to defending ourselves from ideas which in the past led to a barbarity which humanity - with the determined effort of communists - defeated."