Left-wing parties decry the lack of public debate on move to speed up naturalisation of immigrants.
The fate of millions of immigrants is at stake as Italians vote in a two-day referendum that proposes to speed up the process of acquiring citizenship for foreigners who legally entered the country.
The referendum also seeks to roll back labour reforms to provide enhanced job protections.
Polling stations opened on Sunday at 7am local time (05:00 GMT), with results expected after polls close on Monday at 3pm (13:00 GMT).
The measures – backed by opposition parties, labour unions and social activists – are aimed at revising citizenship laws to help second-generation Italians born in the country, to non-European Union parents, integrate more easily.
