If we halved migratory flows "in five years we would lose population equivalent to that of Turin", Boeri said referring to the country's important northern industrial hub.
If immigration were reduced to zero we would lose "700,000 people under 34 years of age in the space of one parliamentary mandate", he told the lower house of parliament.
Italy is suffering a demographic decline with one of the lowest birthrates in Europe. Boeri said he was concerned that "no one seems to care" about this decline in Italy and recommended maintaining a flow of legal migration, which alone, he said, could ensure the balance of Italy's pension fund.
The pension chief added that the Italian economy needed an immigrant workforce to undertake unskilled jobs that Italians did not want to do.
His comments, however, drew a withering response from Salvini who has promised to sharply curb migration and speed up deportations of illegal migrants. In a tweet Salvini accused Boeri – an economist appointed by the previous centre-left government – of "continuing to play politics".
"Where does he live, on Mars?", he added.
Boeri also warned against the new populist government's proposed pension reform which would allow Italians to retire earlier. He said the new plan would cost between €18 and 20 billion a year and suggested it would be better to relax the old pension law – which had significantly raised the retirement age – and which the new government wants to abolish.