Venice will deploy six stewards in St Mark's Square to prevent tourists from stripping off their T-shirts, taking a nap or dropping fast-food wrappers in the piazza that is a UNESCO World Heritage site.

Bordered by St Mark's Basilica, the Clock Tower, the Doge's Palace and the Grand Canal, the square is one of the world's biggest tourist attractions.

Wealthy tourists to the square sip their espresso in style at the Cafe Florian, which dates from 1720 and was frequented by Goethe, Casanova, Byron and Proust. But in the pricey city many more opt for take-aways.

However, the mayor does not want Coke cans and chocolates wrappers in the piazza that Napolean called 'the drawing room of Europe'.