It is perhaps the most recognisable vista in Venice, a 900-year-old piazza that is one of Italy's most beautiful squares, a space supposedly once described by Napoleon as "Europe's finest drawing room".

But St Mark's Square in Venice is at risk of turning from drawing room into advertising showroom, as officials move closer to hanging giant electronic advertising screens from the piazza's elegant palaces to pay for restoration work.

With the elegant facades and arcades of the square in urgent need of their first clean-up in 50 years, mayor Massimo Cacciari said the city's empty coffers had forced his hand. "It's not beautiful or ugly, just necessary," he said. "We need to take care of the monuments and art works in this city, and to do that we need a hand from sponsors."

If plans go ahead, the five screens, each measuring 250 square metres, will be suspended in front of drapes hung on scaffolding along the square's facades to hide restoration work that could last more than six years.

The news provoked an outcry from Venice newspaper Il Gazzettino, which said St Mark's Square was turning into New York's Times Square, while Italian art critic Philippe Daverio warned that other famous piazzas in Italy could be next.

"They already tried to cover the Milan Duomo with neon panels 12 years ago," he told La Stampa. "We got that stopped, but now it's starting again."

"This is a lesser evil given that resources are short and monuments are falling to pieces," countered the office of local architectural superintendent in a statement. Officials plan to make €3.6m (£2.9m) from the deal, covering the cost of the works, and promise to approve all advertising before it flickers on to the screens, to avoid "lapses in taste".

The square's tasteful lines have hitherto survived intact for centuries, despite Napoleon taking over one building for a palace after conquering the city and demolishing a church to make way for a new ballroom next door.

But today St Mark's appears to be under siege, suffering from floods which force tourists and residents to walk across planks on the piazza, all the while glancing upwards to look out for masonry which has started to tumble from buildings weakened by the elements and the incessant pecking of pigeons.

The installation of giant screens, more Blade Runner than Bel Paese, is the next step up from the habit of Italian councils of unfurling enormous advertising posters down scaffolding and awnings, particularly in Rome, where glimpses of baroque churches framed by narrow streets are often blocked by three-storey-high images of saloon cars or bottles of aftershave.

Il Gazzettino warned that stock market prices could soon be scrolling electronically down the sides of Venice palazzi, while art critic Daverio said he believed council accountants were often in no hurry to pull down advertising.

"The money prompts greed and I suspect that works get stretched out to fill coffers. It happened at Porta Venezia in Milan where a four-month job lasted two and a half years."

The hoisting of mega-screens selling fast food and soft drinks in St Mark's also has the whiff of double standards after officials previously instituted "decorum" patrols to stop tourists sitting cross legged in the piazza, removing their shirts or pulling out picnics.

The square has, however, had experiences of the kind of disastrous consequences that can occur if maintenance is not carried out. In July 1902, the bell tower of St Mark's Basilica began to crack. It then collapsed. Miraculously only the caretaker's cat was killed. The tower was later rebuilt as a perfect replica.
Backstory

The piazza was built in the 9th century before being enlarged to its current size in 1177. After coffee was introduced from Turkey, 24 cafes were doing business on the square by the 18th century. The original patterns laid out in the square's marble probably acted as a guide to market stallholders setting up. It is the only square in Venice referred to as a piazza. The others are known as Campi. "Everybody goes to this vast square in the evening," wrote Mark Twain after a visit to St Mark's, where he bought wax matches and discovered granita "the first cousin to ice-cream" while listening to the military band. The square inspired the design of the Austin J. Tobin Plaza at the World Trade Centre. It figured in at least a dozen movies, including Casino Royale and Don't Look Now.