“I call for a vote of members…on my role as political leader because it is right that you are the ones who express an opinion. If something needs changing within the movement, we’ll do it.”
The quietly-spoken Mr Di Maio, a former football stadium steward from a town near Naples, has been totally eclipsed by the rambunctious Mr Salvini since the coalition came to power last June.
Cartoonists in the Italian press portray him as an eager lapdog waiting on the every need of the League leader, who is portrayed in a black shirt and tasseled fez – symbols of Fascism.
The League has seen its support soar after Mr Salvini ordered the closure of Italian ports to NGO vessels that rescue migrants and refugees in the Mediterranean.
If Mr Di Maio is voted out, it is not clear who would replace him.
But in any case, Five Star is on the back foot.
Mr Salvini has for months behaved as if he is prime minister, elbowing aside not only Mr Di Maio but also the actual prime minister, Giuseppe Conte, a former lawyer who was chosen as a neutral mediator between the two very different coalition partners.
There is widespread speculation that increasing tensions between the League and Five Star could lead to the fall of the government and fresh elections, possibly in late September.