According to the AFP, City assembly member Imma Battaglia said she and mayor Ignazio Marino had intended to send a message with the multi-coloured lights, which were switched on Friday in Via del Corso.
Ms Battaglia said the lights symbolised a fight against homophobia after the recent suicide of a gay 14-year-old in the city.
She said: “That is how we came up with the rainbow flag idea,” and added they could also be seen as a “peace symbol.”
However, the far-right Fratelli d’Italia party has condemned the idea, calling it “provocative and ideological.”
Assemblyman Fabrizio Ghera said: “There should be an Italian tri-colour instead.”
The Italian flag colours were used in 2011 to mark the 150th anniversary of Italian unification. Last year, they were monochrome white.
Laura Rossi International, the company behind the rainbow-themed lights, attempted to defuse conflict on Friday by claiming they would now be dedicated to the late Nelson Mandela, who passed away on Thursday.
A spokesperson said: ”This way the message of love, tolerance, unity and sharing will become stronger.”
The teenager to whom the lights originally paid tribute killed himself in August after leaving a suicide note which read: “I am a homosexual, no one understands my drama and I do not know how to make it acceptable to my family.”
Back in July, the Lower House of Italy’s Parliament announced it was set to begin debating a bill that would make homophobic discrimination a criminal offence in the country.
Italy currently has no protections against anti-gay discrimination in public, in the provision of goods and services or against hate speech.
Same-sex marriages and civil partnerships are currently not recognised and same-sex couples do not have adoption rights.
Gender identity is also not a part of official anti-discrimination legislation.
Source: Italy: Rainbow-themed Christmas lights blasted as ‘provocative and ideological’