62-year-old old art critic and councillor Vittorio Sgarbi was furious when the avant-garde tree was put up without consulting him and lambasted the conical grey steel and glass structure as "a useless, immoral and ugly thing," La Stampa reported
Sgarbi - an art critic and former mayor in Sicily who is well known for his disdain of contemporary art - became Urbino's council member for culture in June 2014 with a specific mandate to protect the artistic and cultural integrity of the town's historical centre.
But after the council put up the modern 'tree' in Piazza della Repubblica, Sgarbi accused the city's deputy mayor, Francesca Crespini, of going behind his back to install it.
Sgarbi then threatened to resign if the structure wasn't taken down and proved to be as good as his word by stepping down on Monday.
In his resignation letter, which he published on Facebook, the councillor wrote that he couldn't “share the inconsistent political choices and violations of protocol," and called the tree "a penis that disfigures the city."