Thousands of protesters are to throng the streets of Florence tomorrow before a local referendum on a new tram system that some conservationists say will cause irretrievable damage to the city's mediaeval and Renaissance treasures.

The first rails for the new €715million (£530 million) tram system — designed to cut congestion and pollution in the centre of the city — were laid in October despite the protests. One of the three planned tramlines runs past the Duomo (cathedral) — with its 15th-century dome by Brunelleschi — the adjoining belltower, known as Giotto's Tower after the artist who designed it in 1334, and the Baptistery, celebrated for its bronze doors and 13th-century mosaics depicting The Last Judgment.

Paolo Bonaiuti, a Florentine who is spokesman for Silvio Berlusconi, the centre-right leader, told The Times that the project was “complete madness”.

“It will ruin one of the world's most cherished cathedral squares, not only because of the overhead cables but because of the vibrations. Modern supertrams are more like huge trains,” he said.

The referendum follows a petition organised by Christian Democrats on the centre-left-dominated city council and signed by 13,000 residents. Franco Cardini, a mediaeval historian, said that the project was “a grave mistake”.

Antonio Paolucci, who until recently was head of museums in Florence and now runs the Vatican Museums in Rome, said he was not against trams as a means of public transport, but “I strongly object to them passing so close to the symbolic heart of Florence”. Professor Paolucci said that the solution was to pedestrianise the centre and ban trams and buses.

But Giorgio Bonsanti, Professor of Art Restoration at Florence University, said that visitors and residents needed to move into and around Florence. Trams offered a solution that would “save our monuments, not damage them”, he said.

Professor Bonsanti insisted that there was no risk to the buildings or artworks from vibrations. “I don't understand all this fuss when thousands of often old and noisy buses have been passing the cathedral piazza every day for decades” he said. Centre-right politicians on the council were exploiting the issue for political purposes at a time when Italy was facing national elections in April, he said.

Raimondo Innocenti, Professor of Architecture at Florence University, said that the protesters had offered “no viable alternative”.

Florence city council said that it had done “the absolute maximum” to limit noise and vibrations by using “state-of-the-art technology”, with the rails mounted on a “floating platform” sunk in concrete.

Leonardo Domenici, the mayor, said that urgent measures were needed to reduce the estimated one million cars a day that clog the city's streets. He admitted that hundreds of trees were being cut down to make way for tramlines, but said new ones would be planted.

Environmentalists and conservationists are divided, with the heritage organisation Italia Nostra opposing the 32m-long trams and Legambiente, the leading Italian “green” lobby, supporting it. The council said that although Sunday's referendum was consultative rather than binding, it would “take full account” of the result.

The system envisages three inter-linking lines connecting the centre of Florence with the airport and main railway station at Santa Maria Novella. Critics say Line Two, which passes the Duomo, will also run perilously close to the Galleria dell Accademia, which houses Michelangelo's David. Conservationists say that it may have to be moved.

Officials said that the city attracted “increasingly unsustainable” numbers of tourists, with the statue of David being admired by 1.3 million a year.

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