The amendment to the 'Competition bill' targets well-known bloggers and so-called influencers who use their social media channels to promote products, often without letting their fans know they received payment for the publicity.
Featuring brands in their Facebook, Instagram or Twitter posts can be extremely lucrative for those with large followings.
The new bill would obligate the government to regulate this kind of advertising, by introducing new rules ensuring adverts are always clear to viewers. Such rules are already in place in the UK and US for example, where influencers must mark paid-for posts with '#ad' or 'sponsored'.
"This kind of publicity is promoted in a concealed way, and isn't always distinguishable [from normal posts] to consumers," said Democratic Party deputy Sergio Boccadutri, who proposed the amendment relating to sponsored content following lobbying Italy's National Union of Consumers, which has long campaigned for regulation of the sector.
Some Italian newspapers dubbed the move an 'anti-celebrity law', with many singling out top fashion blogger Chiara Ferragni as one of the main culprits of covert sponsored selfies.
The 30-year-old blogger regularly uses her Instagram account to showcase products she has a stake in, or which has been paid to promote by other brands. But while Ferragni regularly uses the hashtag '#ad' in sponsored posts, not all her peers do the same, and there is currently no regulation in Italy.
This Christian Dior outfit has appeared in several of Ferragni's Instagram posts.
"Our goal is to have clear rules; next to each sponsored post, there should always be a caption properly informing consumers of the promotional nature of the message," the National Union of Consumers said on Thursday.
The Competition bill - which also included clauses relating to telemarketing, insurance, pensions, the finance and tourist sectors among others - was passed with 218 votes in favour, 124 against and 36 abstentions. It must now be passed in its current form by the Italian Senate in order to become law.
Making sponsored posts clear would not only help with transparency, allowing consumers to know when they're seeing an advert, Boccadutri explained, but would also help Italy's tax authorities as it would be clearer when stars had received payment.