The radical left in Spain (including even the Anarchists who were a significant poltical force at the time) supported the Republican government. The purges that took place on the left, were the purge of the POUM (Trotskyist, the group Orwell fought with) and then the CNT-FAI (anarchist) by the Communist party (Stalin/USSR). Both purged groups were considered to be to the Left of Stalin by all sides in the conflict, the purged groups certainly were definitely less authoritarian.