Leandro Comacchio, a Northern League leader, is outside a suburban supermarket in Padua collecting signatures for a referendum to stop the construction of a mosque. The campaign, he claims, is not aimed at Muslims. It is, rather, a protest against the “permissive” centre-left council which, he alleges, is giving away council land for construction of the 2,300sq ft mosque.

He contends that the council tolerates unchecked immigration, which has in turn exacerbated street crime, urban decay and drug dealing.

Immigration, and the perceived crime spree, has become a key issue in the city once best known for its ancient university and elegant piazzas – so much so that Northern League supporters have set up vigilante groups.

“We have formed citizen street patrols, together with residents’ associations,” Mr Comacchio said. “A minimum of four people, but often up to ten, all with phosphorescent jackets carrying the Lion of St Mark, the symbol of the Veneto region.”

Mr Comacchio does not like the term vigilantes, prefering instead “concerned residents” who call the police when necessary.

Muslims at the provisional mosque in a derelict supermarket on the other side of town are feeling under siege. The mosque, which has to close by next month because the owner is reclaiming the site, is next to Via Anelli, a dilapidated immigrant housing estate, around which the authorities erected a metal fence – the Wall of Padua – in an attempt to contain drug dealing and prostitution two years ago.

Maher Selmi, a Moroccan student who is the mosque’s spokesman, said that there was worrying prejudice against foreigners as Italy shifted to the Right.

In national elections last month a centre-right coalition led by Silvio Berlusconi, which included the separatist Northern League and the “postFascist” Alleanza Nazionale, swept the board. Gianni Alemanno, also of Alleanza Nazionale, was elected Mayor of Rome this week.

“We don’t want confrontation,” Mr Selmi said. “We want dialogue with all parties to find common ground.”

The League, led by Umberto Bossi – who once said that those arriving by sea should be fired on by the navy – doubled its national vote to more than 8 per cent. In Padua, where this week there was an outcry when a teacher was suspended for telling Muslim schoolgirls to take off their veils, it tripled its vote from 5 per cent to 15 per cent, according to Mariella Mazzetto, a Northern League councillor.

Last year Ms Mazzetto took a pig to the abandoned farmhouse where the mosque is due to be built next to a nomad encampment. Pork is anathema to Muslims but Ms Mazzetto denies that she or the League are racist or xenophobic. “I made a provocative gesture with the pig to arouse debate,” she said. “The League has grown in strength because it is in tune with concerns of ordinary people.”

The campaigners, who need 5,000 signatures to force a referendum, have so far collected more than 1,600.

Flavio Zanonato, the centre-left mayor, said he was confident that Paduans would support the €860,000 (£670,000) mosque, which the Muslim community would fund by paying rent to the council. Maurizio Conte, a League leader in the Veneto, said that the mosque would attract “uncontrollable criminals and fundamentalists.”

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