Matteo Salvini, who heads a coalition that topped the polls in last month's general election, took to Twitter to note that "today is International Roma Day".
His comment was that, "if many of them worked more and stole less, if many of them sent their children to school instead of teaching them to steal, then it really would be something to celebrate".
Mr Salvini, 45, hopes that the performance of his anti-immigration League will help him ultimately become prime minister despite the lack of a clear majority after the March 4 vote.
Italian President Sergio Mattarella is due to meet political leaders in the coming week to thrash out the shape of a new government.
Pope Francis told worshippers in St Peter's Square meanwhile that he hoped Roma Day could foster greater understanding of Roma culture through the "goodwill of getting to know one another" and "mutual respect".
"This is the path which leads to true integration," the pontiff said.
Although over half the 170,000 or so Roma and Sinti people in Italy are Italian citizens with regular jobs and houses, some 40,000 of them are housed in purpose-built camps, according to 2015 figures.
Hate crimes against the poorest Roma are rife.