Some 30,000 Filipinos without proper papers will be deported from Italy.
Ambassador to Rome Philippe Lhuillier said undocumented Filipinos and other illegal aliens would be detained before they are deported.
The Italian government is set to crackdown on illegal aliens within the next few days, he added.
The Department of Foreign Affairs (DFA) estimates some 33,276 out of 170,000 Filipinos in Rome and Milan are illegal residents.
Earlier, 40,000 illegal Filipinos in Japan were reportedly arrested after Japan's immigration law was amended to make it a criminal offense to illegally stay in the country.
Under the new law, illegal aliens would be imprisoned or be made to perform hard labor for not more than three years, or pay a fine of 300,000 yen.
Back in Italy, Lhuillier said human rights groups and politicians are questioning the constitutionality of the government practice of detaining illegal aliens.
He said Italy will launch the crackdown in preparation for a new law requiring a quota of 63,000 immigrants for countries outside the European Union.
However, the restrictions will not apply to foreigners who are already in Italy when the law gets passed, he added.
Lhuillier said Italy's interior ministry has assured that more immigrants can enter Italy after six months or a year if the first 63,000 get employed.
Immigrants would be allowed only if directly hired by the employer or if a resident of Italy guarantees their accommodation and living allowance for a year, he added.
He said the new law requires that preferential quota be given only to countries that have concluded readmission agreements with Italy.
Lhuillier recommended that the DFA immediately act on the proposed Philippine-Italy Readmission Agreement.
Last year, Italy granted amnesty to 123,000 out of 250,000 illegal aliens, while the rest have been deported, he added.