Grillo's comments drew widespread condemnation from the Italian media world - in no small part because as leader of the upstart, anti-establishment Five Star Movement (M5S), Grillo himself has been accused of being at the centre of a news network that promoted false or misleading stories.
In late November, BuzzFeed News asserted that members of Grillo's party had "built a sprawling network of websites and social media accounts that are spreading fake news, conspiracy theories, and pro-Kremlin stories to millions of people".
Grillo later denied the accusations strongly. "The charges of making pro-Kremlin propaganda or spreading false news are ridiculous," Grillo wrote in his own blog, one of the most popular in Italy. However, BuzzFeed noted that even Grillo's blog has spread misinformation at times - such as sharing a picture of an audience waiting to hear Pope Francis and saying it was an anti-government protest.
Grillo's argument for a "popular jury" appeared to have been sparked by a number of Italian politicians who have said that a government body is needed to battle the problem of misinformation on the Internet. The M5S leader, who draws much of his support online, said Italian newspapers have published a number of false stories about him without apologising.
"Newspapers and television news programs are the top fabricators of false news in the country, with the aim of keeping power for those who already have it," he said in his blog post. Grillo also pointed to Italy's relatively low ranking - 77th - in a recent press freedom index.
A number of Italian journalists have responded angrily to Grillo's suggestion: Enrico Mentana, news director of the TG La7 television channel, wrote on Facebook that he planned to sue Grillo, who had included La7's logo in an illustration on the blog post. Mentana later withdrew his threat after Grillo said he wasn't talking about La7 specifically.
Grillo's M5S was one of the driving forces in opposition to Italy's constitutional referendum in December. It has begun campaigning for Italy's upcoming general election, which is expected to be held soon.
Matteo Renzi resigned as prime minister after his failed attempt to change the constitution. Some polls have shown that M5S is the most popular party in Italy.