Grillo's Five Star Movementwas the biggest surprise in February's general elections, drawing around 25 per cent of the votes with pledges to clean up politics.
But since then, it has been dogged by infighting - extensively reported by media - and fared badly in recent local polls.
"Journalists should not be allowed to infest the Chamber (of deputies) and the Senate and move around freely. They should be confined to dedicated areas, outside the palaces," Grillo wrote on his blog.
The satirist has a fraught relation with journalists, and accepts interviews only with foreign media, claiming that domestic ones are biased.
On his instigation, the M5S expelled last week senator Adele Gambaro, after she criticized him on TV.
Grillo, a stand up comedian turned activist, did not run for parliament and rejects the title of M5S leader, claiming to be merely its spokesman. His blog messages carry weight among supporters and set the party line.
He attacked "gossip hunters and hacks" who chase lawmakers "in staircases or in the toilets," rather than "ask for an appointment," and proposed to put up a sign outside Italy's legislative chambers: "No gossip. Parliament is not a brothel."
Voice of Russia, dpa