Tito Boeri also warned that government plans to reform the pensions system would be much more costly than coalition parties were predicting, saying demographic trends meant that even the existing system was unsustainable.

Italy’s new interior minister, right-wing leader Matteo Salvini, who has promised a severe crackdown on illegal immigration and mass deportations, accused Boeri of playing politics. “Where does he live? Mars?” Salvini wrote on Twitter.

Boeri, a university economist who was appointed pensions chief by the previous center-left administration, told the INPS annual conference that current forecasts pointed to Italy having just one worker per every pensioner by 2045.

“To maintain at a sustainable level the ratio between those who receive a pension and those who work, the number of immigrants is crucial,” Boeri said.

He said that if recent demographic trends continued, the Italian population would shrink by 300,000 within the next five years.

“It is as if a city like Catania disappears,” he said, referring to the second largest city in Sicily.

“By halving the migratory flows in five years we would lose, in addition, a population equivalent to that of Turin,” he added, referring to one of Italy’s main industrial cities.

He said Italians were badly informed about the number of migrants living in the country, with locals on average claiming migrants made up 26 percent of the population, against the real figure of just nine percent.

“The difference between perception and reality is much more pronounced here than elsewhere. It is not just prejudice. It is real disinformation,” he said.

He also took aim at government plans to re-write a 2011 pension reform, that was named after then-Welfare Minister Elsa Fornero and which called for hikes to the retirement age.

The government is looking to introduce a system whereby someone’s age and the number of years they have worked are added together, with pensions available when the total reaches 100.

It has said this change will cost some 5 billion euros a year, but Boeri predicted the true figure would be around 18 billion euros.

He added that “it was not possible” to turn back the clock on the Fornero reform, but said it could be made more flexible.

Boeri’s four-year mandate is due to expire in early 2019.