Pedestrians pass by a Banca Monte dei Paschi di Siena bank branch in Siena, Italy.

Recapitalization of Italy's troubled banks will be harder following the failure of a referendum pushed by Prime Minister Matteo Renzi, with ratings agencies among key actors to watch as delays may loom as the country likely heads to early polls next year.

Renzi resigned after failing to win a mandate to curb the powers of the upper house legislature, throwing into question measures including plans by Banca Monte dei Paschi di Siena to conduct a 5 billion euro ($5.3 billion) capital increase this week, a solution backed by the outgoing premier.