MILAN, Dec 5 (Reuters) - A 5 billion euro ($5.33 billion) rescue plan for Italian bank Monte dei Paschi di Siena BMPS.MI hung by a thread on Monday after Prime Minister Matteo Renzi's heavy defeat at a weekend referendum tipped the country into political turmoil.
The bank, saddled with bad loans, needs to raise the money by the end of the month to avoid being wound down, but Italy now faces early elections after Renzi said he would quit to take responsibility for the defeat of his constitutional referendum.
Monte dei Paschi, rated the weakest lender in European stress tests this summer, had planned to secure a firm commitment from one or more anchor investors and launch a share sale as early as Wednesday or Thursday.
The lender's shares fluctuated wildly in early Monday trade, with investment banks due to meet at around 1100 GMT to decide whether to back the cash call. Under a pre-underwriting deal, they can drop the transaction due to adverse market conditions.
The bank's board was expected to convene on Tuesday.
Renzi announced he would step down in the early hours of Monday after his constitutional reform was rejected by 59.1 percent of voters, a wider margin that had been expected.
Italian government bonds and shares fell sharply early on Monday, as investors worried that instability in the euro zone's third-largest economy could reignite a dormant financial crisis and deal a hammer blow to the country's fragile banking sector.