A couple of resting tourists look baffled as they are shooed away from the steps of the portico that surrounds St Mark’s Square in Venice. They are the first victims of the so-called “angels of decorum”, a group of stewards who started monitoring the canal city’s most congested areas on Friday morning for signs of uncouth behaviour. It appears to be a somewhat futile task: in a city that brings in about 60,000 tourists a day, unwitting counterparts soon replace them.

Still, as lunchtime nears, the couple fare better than those who settle on the steps and commit a far worse infraction. “Sitting down is forbidden but sitting down and eating is doubly forbidden,” Issa Diop, who is on his fourth summer season as a steward, tells the Observer.

The creation of the team of 15 is part of an overall plan by the Venice authorities to restore dignity to a city whose reputation has been tarnished by misbehaving tourists. Visitors have often been photographed bathing or peeing in a canal, or leaping drunkenly from the Rialto bridge into the pungent waters below.

Dressed in white vests with #Enjoy Respect Venezia emblazoned on the back, the stewards are on the lookout for anybody committing such transgressions – along with those parading around bare-chested or in bathing suits, feeding pigeons, dropping litter or huddling on bridges in groups. They must also ensure that tourists keep to the right when walking along the city’s narrow alleyways so as not to block the flow.

The rules have long been in place and are listed on signposts dotted around the square. In the English version they come under the word “Forbid” (sic). But few people have taken note.

“It’s about respecting the city,” said Paola Mar, Venice’s tourism chief. “If you go to Singapore and throw a cigarette butt on the floor, you’d soon be in handcuffs. We don’t want to be like that but people do need to respect the rules.”

Tourism chief Paola Mar explains that the latest moves are about “respecting the city”. Photograph: Chris Warde-Jones/The Observer

It isn’t all about ticking off tourists, though. The stewards, who are required to speak English, also have a duty to tell visitors where they can eat their picnics while encouraging them to try the local cuisine. They are seen as gentle assistants to the local police, who have the authority to bar people from the city and hit them with fines of up to €300 for flouting one of the more serious rules reinforced by authorities last week.

These include bans against bathing or simply dipping your feet in the canals; the latter misdemeanour is said to have been a favourite pastime of artists and writers, including the American author Henry James, who frequented Venice when it was regarded as La Serenissima, the most serene.

Authorities believe that outwardly drunken behaviour has spoiled the serenity of today’s Venice – so much so it will no longer be tolerated. Hen and stag parties have been banned while the kind of raucous behaviour that might come with, say, celebrating a graduation, will also be frowned upon.

“It’s not about criminalising one particular group – we don’t want to see locals drunk either. The rules against rudeness apply to all,” said Mar.

But in an emotionally-charged city where residents often jar against their leaders, the latest actions are seen as a joke. “There are far bigger problems to deal with than criminalising tourists for sitting down, cooling their feet in the water or eating a sandwich,” said Marco Gasparinetti, who leads the city’s Gruppo Aprile 25 activists.

Residents’ associations such as his have long complained about the authorities’ inability to manage a tourism industry which they argue has eroded their quality of life as well as damaging the environment and, they suggest, driving residents away: Venice’s population has fallen from about 175,000 in the post-second world war years to 54,000 today. The city loses some 1,000 inhabitants a year.

They also lament the behemoth cruise ships that chug through the Grand Canal, emitting fumes and disgorging thousands of people into the crowded streets – on some days as many as 44,000. It was announced in November last year that the largest vessels would be diverted from the city centre, but the plan is yet to be officially approved by the national government.

Gates were installed at the two entry points to the lagoon over the 1 May national holiday weekend in an attempt to ease the throng heading towards St Mark’s Square and the Rialto bridge. They will be used again from now until the end of August.

Issa Diop at work during the stewards’ first day on duty. Photograph: Chris Warde-Jones/The Observer

If numbers get too high, the gates are closed and access is allowed only to those with hotel bookings or holding a Venezia Unica pass, a card that is mainly used by residents but can be bought for €14 by anyone who uses a water bus.

“Again, it’s just a marketing tool to show they are doing something,” added Gasparinetti. “It doesn’t resolve anything.”

Authorities are also trying to encourage people to visit other, lesser-known areas of the Venetian lagoon or one of its other islands, such as Murano and Burano.

But Gasparinetti is not impressed, likening this particular strategy to spreading tomato sauce. “By spreading the problem everywhere there is nowhere to find peace,” he said. “We don’t see how this will improve our quality of life.”

He also pointed to the hotels under construction in the nearby urban sprawl of Mestre, with the idea being to encourage people to visit nearby places, such as the beach of Jesolo.

“They don’t come here for Jesolo, they come for Venice,” he added. “So even if they stay in Mestre, they can reach Venice in 10 minutes.”

The divergent opinions between residents and the tourism authority can perhaps be best summed up in their comparisons of the city to Disneyland – the first seeing the Florida theme park as a nightmare, and the latter as a dream.

“Maybe these people don’t know Disneyland, but I do, having been there 13 or 14 times for work,” said Mar. “Disneyland is perfect and clean and works extremely well.”

In a city that survives on tourism, her priority, she added, is to manage the flow while developing a plan that will encourage people to stay longer and experience Venice beyond the main sites. Of complaints from residents, she says: “Italy is a funny place… if you don’t do anything then it’s not good, but if you try and do something, it’s still not good.” .

Back at St Mark’s Square, among those being reprimanded by the stewards is a Belgian family sitting on the portico steps and eating sandwiches from a nearby shop. With no benches on the square, their only other option would have been to go to one of the local cafés where a cappuccino can cost up to €12.

“It’s ridiculous,” says Rebecca Calewaert, travelling in Italy with her husband and two children. “Why sell sandwiches to take away if we can’t eat them here? We’re adults and would have thrown away our rubbish. Surely there are more important things to focus on, such as pickpockets.”

Meanwhile Venice resident Barbara Miccoli, fully aware of the patrolling vigilantes, snaps a photo of her son blatantly breaking two of the rules: eating a sandwich and simultaneously feeding a pigeon.

“Yes, the city does need to be respected,” she says. “But these rules are a little exaggerated.”