The explosion in the number of banners being hung from balconies comes as the social-media obsessed anti-immigrant leader is frantically campaigning ahead of next week's European parliamentary elections.
The previously sporadic protests became a wave after authorities in northern city Bergamo on Monday asked fire fighters to remove a banner reading "You're not welcome."
The move in broad daylight was filmed and went viral, prompting more than 200 similar protests ahead of a Salvini election rally in the central city of Campobasso on Wednesday.
On Thursday, banners in southern city Naples greeted Salvini, who is also interior minister, ahead of a security meeting there.
"Salvini go home!", "Naples doesn't want you!", "No to the minister of hate", read some of the banners hanging from the city's famed balconies.
Salvini often derided southern Italians before his northern-separatist party became a national entity.
"The bumpkins don't forget!" read another banner, using a derogatory Italian word that Salvini previously used against southerners.
"When are you going to work?" asked other banners, after Italian daily La Repubblica revealed this week that Salvini had spent just 17 full days at his ministry so far this year.
Other banners goaded the nationalist about the 49 million euros of misspent public money that his party is supposed to pay back in instalments, or the Zorro toy Salvini revealed this week was stolen from him as a child.
"Some of the banners make me laugh," Salvini said on social media on Wednesday.
"I'll buy a coffee for the most ironic one," he said, while criticising the 126 graffiti authorities have counted calling for him to be killed since the start of the year.