Virginia Raggi, 37, also becomes the city’s youngest ever mayor after winning 67 per cent of the vote during a run-off election, two weeks after an initial round failed to deliver an outright winner.
Beppe Grillo, founder of the populist Five Star Movement, of which she is a member, is a political ally of Nigel Farage in the European Parliament and has called for Italy to hold a referendum on whether to return to the lire.
While Ms Raggi has quietly dropped that stance, the appointment of a Eurosceptic will add to the growing panic across the continent at the prospect of a Brexit.
Although Euroscepticism is on the rise, according to recent surveys, most EU members do not want to leave the Union. Small countries are also fearful that a British exit would deprive them of key allies against bigger nations with federalising instincts.
Politicians and newspapers in those countries were yesterday begging British voters not to choose Leave. Aftonbladet, a Swedish tabloid, joined a chorus of concern about the so-called contagion risks of a Brexit that many in Europe fear could spark a wider unravelling of the European Union.
“We should not panic, but we are waking up to a new political reality,” said Stefan Lofven, Sweden’s prime minister, in a speech calling for calm. “We don’t know exactly what impact and what forces it can trigger in Europe.”
In Denmark, Lars Lokke Rasmussen, the country’s prime minister, fended off calls for a referendum in Denmark from the Danish People’s Party. “I want no such referendum. Denmark belongs to the EU. We do today, and will next week as well, and this is the case totally regardless of what the outcome is of the vote in the UK,” he said.
Antoni Macierewicz, the Polish defence minister said recently that a Brexit would “change the balance of powers in Europe”, stoking demands for “more Europe” that would make life “more difficult” for counties like his.
The appeals for unity were echoed by Donald Tusk, president of the European Council: “I appeal to the British citizens: stay with us. We need you.”