On March 23rd 2005, Venice lost another iconic view: that of the beautiful gothic façade of Santa Maria della Carità, which forms the most visible part of the Gallerie dell'Accademia. First the structure was acupunctured with scaffolding. Then it was swaddled in plastic sheeting. Large, powerful spotlights were added to the scaffolding. It turned out that these were for the advertising billboards. And these weren't just any billboards. They were the kind now known in Venice as "maxi-pubblicità": cinema-screen sized advertisements that often display a violent taste disconnected with the contents of the historic structures they cover. Churches, libraries and galleries have been plastered with the kind of images used to sell alcohol, soft drinks, designer grunge, jewellery and the city's casino - nearly-naked women, garish art in eye-scorching colours and visual innuendo. Some of Venice's most dignified buildings have been reduced to soft-porn pedlars or eyesores, or both. And the brightest lighting in the city illuminates the desecration.

Back in 2005, the contractors' notice announced that the work at the Accademia would continue for '1100 giorni consecutivi'. I'm happy to report that in exactly double that time, the scaffolding has come down and the blaring maxi-pubblicità is no more.

At least not at the Accademia. Sadly, elsewhere in Venice the billboards are still in place. The "Bridge of Signs" has been brutalised this way for years. A similar fate has befallen the facades of the Church of San Simeone Piccolo, the Marciana Library and even the Napoleonic wing of the Correr Museum. We have one next door. Our evenings are polluted by its strident lighting, and we can watch it reflected in the windows of the unfortunate residents opposite.

Seeing the excrescence for the first time, our neighbour exclaimed, 'It makes me ashamed to be Italian.'

The usual justification for the billboards is that they pay for the restoration of historic buildings. Venice is a high-maintenance city, and there's zero funding from Rome. But this stance carefully avoids some painful questions.

Sponsorship for restoration is not new. In better times, buildings under restoration were clad in photographs or drawings of their own facades, with a sponsor's logo discreetly positioned. Why are these sponsors now allowed massive, invasive, floodlit images of their own product instead? Why the vulgar, often sexual imagery? In effect, the sponsors are dictating the visual culture of beloved parts of Venice, even when their tastes are not to Venice's taste. Surely something is out of proportion here, when commercial sponsors are allowed to deface the very thing that they claim to be saving with their money?

"No company sponsoring a concert would get its jingles played in the middle of a Mozart symphony," points out Nelli-Elena Vanzan Marchini, founder of the environmental and social organisation Venezia Civiltà Anfibia.

The questions continue. Why does it cost so little for global brands to buy space seen annually by 17.5 million tourists? (One report says that the Bridge of Sighs costs just 40,000 euros a month). Why do these billboards stay up for years on end? Just how much work is actually going on behind them? Is extended advertising revenue in fact a disincentive to quick progress on restoration? Are we being deprived of Venice's beauty and being forced to look at brash ugliness for longer than we need to be?

Under the auspices of Venice in Peril, last October the Art Newspaper published a letter of protest from a group of the world's leading cultural experts, including Norman Foster, the directors of the British Museum, the V&A and the Museum of Modern Art in New York, the heads of museums in Boston, Dresden, Stockholm and the Hermitage in St Petersburg. They reminded the Italian government that 'Venice is a Unesco World Heritage Site and that a preceding government of Italy undertook to protect its essential nature in perpetuity when it accepted this nomination.' And they asked the culture minister to outlaw the billboards, which "ruin your experience of one of the most beautiful creations of humankind". The petition pleaded the case of the tourists whose spending keeps the Venetian economy afloat, some of whom may have saved for years to fulfill their dream of seeing la Serenissima: '"They come to this iconic city with an image of it in their mind's eye, and instead they see its famous views grotesquely defaced."

In response to the petition, there have been promises of a review, of more attention to be paid to the sensibility of the city and the length of time that the maxi-pubblicità covers up Venice's historic facades. And maybe attitudes are starting to change in the right places. The new culture minister Giancarlo Galan has promised to take matters in hand. He says he wants to look at less impactful involvement by the sponsors. Moreover, he has recently wondered, as I do, if the hated billboards might actually have a negative effect on the companies who pay for them . that people might not want to buy products associated with 'the degradation of the image of Venice.'

Now he's talking. But Galan's 'cry of pain' needs practical expression. What to do? Well, what was wrong with the former façade photos or drawings with the discreet sponsorship logos? If the sponsors' taste can't be trusted, it can and must be regulated. And someone needs to look behind the advertising on every one of these maxi-wrapped buildings - to see if there is any work going on there. If not, then the scaffolds must come down, dragging their billboards behind them.

Personally I like the suggestion made by Roberto Ciambetti, the regional authority's public spending assessor, that assets sequestrated from the mafia could be sold to pay for Venice's upkeep. The mafia is the most discreet of big businesses. The godfathers may be global but they're unlikely to want to raise their brand consciousness with massive posters of their 'product'.

It's pleasant to imagine how quickly those scaffolds would come down if there was no advertising at all in front of them.

To read the whole petition, see Venice in Peril's website