“It has the potential to disrupt policy making and reduce policy continuity, and to weigh further on an already weakening economy,” Fitch Ratings said in a statement.
“The prospect of a lengthy period of political instability following Italian parliamentary elections adds to the pressure on the country’s sovereign rating,” it said.
Fitch scores Italy with an A- rating and a negative outlook.
“If a weak government emerges, it will be less able to respond to economic shocks,” it said.
A centre-left coalition won the most votes in elections failed this week but not enough to form a majority in parliament.
No possible majority coalition has emerged and many analysts warn Italy will have to hold new elections within a few months at the latest.