Ornate stucco reliefs have crumbled from the Trevi fountain, Rome's baroque masterpiece, making it the latest in a series of Italian monuments to suffer damage and reigniting a row over Italy's commitment to protect its heritage.

As hundreds of tourists lobbed pennies into the fountain's pool on Monday, workmen were erecting scaffolding around a section of the facade where fragments of a gargoyle's head and foliage crashed to the ground on Saturday night.

City officials played down the damage, blaming it on Rome's freak snowfall this winter, which caused water infiltration. But as the rest of the fountain was checked for crumbling stucco, Italy's Green party launched a campaign against what it described as dangerous cuts to the funding to maintain Rome's monuments.

"We are asking Romans to tip us off to sites which are not being taken care of," said the Green party president, Angelo Bonelli.

Bonelli cited the Colosseum, where stone fragments fell from a wall last year, and Nero's palace, the Domus Aurea, which has been closed to visitors since a roof collapsed. Archaeologists have also blamed the collapse of a number of walls at Italy's best known dig, Pompeii, on a lack of day-to-day maintenance.

The Trevi fountain, which centres on a statue of Neptune on a chariot and features a cascade of rocky waterfalls, last underwent major works in 1990.

Commissioned in 1732, it attained iconic status when Anita Ekberg waded into its 20-metre-wide pool in the 1960 film La Dolce Vita. In 2007, it ran out of water when the underground Roman aqueduct that still supplies it was blocked by workmen digging a garage.This year, masonry crumbled from the arches holding up two other, disused, Roman aqueducts in the Italian capital, the Acqua Claudia and the Acqua Felix.

"That damage, just like the damage at the Trevi, was due to the heavy snow and rain this winter," said Umberto Broccoli, Rome's cultural heritage superintendent. "Rome is not Glasgow, and buildings were built accordingly," he added.

Broccoli said that previous restoration efforts were also to blame for this weekend's damage at the Trevi fountain. "I climbed up yesterday and saw that lead struts inserted to protect the facade had split."

But he agreed that regular maintenance was key to keeping monuments from falling over. "You need more teams of masons patrolling sites," he said. "The problem is we have so many monuments. The UK has Hadrian's wall, while we have walls around every town to protect."

Sections of the Aurelian walls surrounding the city of Rome, which were built in the third century, have collapsed in recent years, but Broccoli said the walls' builders were partly to blame. "They built in a hurry, right across amphitheatres, tombs and aqueducts, and it already needed restoration by the 4th century," he said.

Obtaining the €75m (£60m) needed to restore the walls would be impossible, he added, unless Rome was allowed to cover the scaffolding with adverts, a solution that provoked fierce controversy in Venice when a huge Coca-Cola billboard blocked views of the Bridge of Sighs.