Padua, Italy: Venetians shunned the fifth vote in 40 years to break away from sister city Mestre on the Italian mainland, with little expectation of a parting of the ways.

Only 18.6 per cent of 206,553 potential voters had showed up at the polls by 6pm on Sunday - a long way short of the 50 per cent required for the referendum to be valid.

Venice and Mestre became a single administration in 1926 when Mestre's petrochemical plant was being built. At the time, the population of Venice and its 11 islands was roughly six times that of nearby Mestre.

A city worker helps a woman who decided to cross St. Mark square on a gangway, in flooded Venice last month. Credit:AP

The situation was reversed in the following decades as new factories created jobs in Mestre while Venetians began to leave a city where life was rendered increasingly hard by mass tourism and frequent flooding.