In the passive voice, the agent (the entity performing the action) is normally introduced by the preposition da (by). However, in formal contexts—such as news reports, official announcements, or negotiations—Italian often expands this to da parte di.
You can use da parte di instead of da to emphasize that the agent is an institution, a collective group, or a formal entity, such as a government, a trade union, or an administration.
Because it ends in di, you must combine it with the definite article of the noun that follows, creating standard articulated prepositions like del, della, dell', or dei.
This structure is extremely common in bureaucratic language and official communications, such as when discussing contracts, press releases, or legal requests.
It is also perfectly suited for collective groups, like workers or management, especially when highlighting the different sides of a formal negotiation.
