A plan for the 1.2m (4ft) barrier, stretching around the front of the basilica, was hatched after flood water surged through the 11th century building in November, smashing windows, soaking mosaics in corrosive salt water and submerging the crypt to a metre’s depth. It has now received preliminary permission from city officials.

“The barrier is essential and feasible and we aim to get in place by November, when we fear that high water will return,” Pierpaolo Campostrini, a basilica official, told The Times.

Propelled by wind and tide, flooding reached 1.87m above the normal level of Venice lagoon last November, the highest since 1966 when thousands of people left the city.

Facing St Mark’s square, the lowest point in Venice, the basilica is particularly vulnerable, with repairs for the recent damage estimated at €5 million.

Seeping seawater gets beneath the floor mosaics buckling them and rises through the brick walls, causing marble panelling to bulge outwards.

Church officials want a barrier 150m long and costing €3.5m. If approved by the city’s cultural superintendent, it would stand 2m from the basilica wall.