Maurizio Gasparri, a senator with Silvio Berlusconi's conservative Forza Italia party, is well known for his polemical verve and has earned the title of "cyber-bully" for his vigorous use of social media.
In August 2013 he was drawn into a Twitter debate about the political and economic record of former President Carlo Azeglio Ciampi and saw red after one of the other participants recalled a gaffe in which Gasparri allegedly revealed his ignorance of the banking sector.
Gasparri responded with a private tweet that could be translated as: "Arrogant ignoramus you make me vomit."
The recipient of the message was Riccardo Puglisi, an economics researcher at the University of Pavia.
Puglisi relayed the message publicly on Twitter and subsequently lodged a complaint with the Justice of the Peace in his home city.
Gasparri is due to appear before the magistrate in Pavia on Sept. 21, accused of violating a law that punishes anyone who "offends the honor or decorum of a person who is present, or via telegraphic or telephone communication."
The crime is punished by up to six months imprisonment or a €516 (US$562) fine.
There have been several cases in Italy where people have been sued for defamation for messages published on Facebook and Twitter but this is the first time someone is to be prosecuted for a private message on Twitter.
In another case from 2013 the journalist Gianni Riotta was threatened with a defamation lawsuit for retweeting a critical article in another newspaper about a lawmaker from the Five Star Movement.
Gasparri dismissed the case as ridiculous and said he didn't expect the judicial authorities in Pavia to take it forward.
If they did, he told the Corriere della Sera newspaper, he would review the large number of insults he had received himself and consider taking action against those responsible for them. "I could have an income for life from all the insults I have received," he said.
Puglisi was unwilling to be drawn on the case, but told an online publication: "Mine is a very limited thing. But I believe one has the right not to be insulted."