CERNOBBIO, Italy—President Giorgio Napolitano of Italy made a forceful call Saturday for a "true political union" in Europe, saying the idea "is no longer a taboo," as other European officials said they worried about a growing cultural divide in the region.

Addressing European Council President Herman von Rompuy and other officials gathered at a conference here, Mr. Napolitano called for a faster move towards flanking Europe's single currency and intertwined banking system with democratic unity as well.

That...