Luca Morisi has been placed under investigation by Verona prosecutors but has denied any wrongdoing.
The man behind the social media campaign of Italy's Matteo Salvini has quit his role over a drugs inquiry.
Luca Morisi was placed under investigation by the Veneto Prosecutor's Office over suspected narcotics offenses.
"Morisi has been entered in the register of suspects for the alleged transfer of narcotic substances," Verona's public prosecutor Angela Barbaglio told the ANSA news agency.
"The nature of this [offense] is still awaiting the outcome of an investigation," he added.
After a search of his house, small samples of drugs were found, and mobile phones were seized, according to Italian media.
Morisi had left his post earlier this month as the head of social media communication of the leader of the League party citing "personal issues". He has denied any wrongdoing.
In a post on Facebook, Salvini said that Morisi had "hurt himself more than others."
"When a friend makes a mistake and makes a mistake you don't expect ... first you get angry with him and very angry. But then you reach out your hand to help him up."
"Friendship and loyalty for me are life," Salvini added, alongside a photo of the two men.
The far-right party leader has become well-known in Italy for his extravagant social media profiles and strategy.
Morisi was even known as "The Beast" due to his aggressive comments online towards political opponents.
His departure from the League comes as the party is falling in the polls, after criticism for its support of a mandatory COVID-19 "green pass".
Italy is due to hold local elections in several major cities -- including Rome, Milan, Turin, and Naples -- next Sunday.