The number of Muslims in Italy has rocketed from about 2,000 in 1970 to nearly two million at the end of 2015.
Academics say the number is expected to continue to rise as migrants from Africa and the Middle East continue to arrive.
Sociologist Massimo Introvigne, director of the Centre for New Religions Studies (Cesnur), branded the number “shocking”.
He said: “This number is shocking also because in 1970 there were only between 2,000 and 3,000.” Mr Introvigne said the number of Muslims in Italy is growing rapidly.
Islam is the second biggest religion in Italy behind Catholicism.
There are only four official mosques registered with around 2,000 unregistered mosques across the country.
In a bid to ease relations between the Italian authorities and Muslims, Italy set up a Council of Italian Islam to improve integration.
But despite being home to Europe’s largest mosque – the Great Mosque of Rome – Islam is not formally recognised by the state leading to a surge in underground places of worship.
