Italian banking stocks came under renewed pressure on Friday on growing jitters before the Dec. 4 referendum on a constitutional reform which could unseat Prime Minister Matteo Renzi.
Italy's bank sector index .FTIT8300 fell as much as 4.2 percent to its lowest level since October 5, weighed down by losses in bank heavyweights UniCredit and Intesa Sanpaolo.
Both banks are also suffering due to worries they may need to set aside more money against bad loans.
Recent polls suggest that Italians may reject the planned reform and Renzi has said he will resign if he loses. Investors are concerned his departure would make it harder to fix the country's bank problems.
Deutsche Bank has forecast that banks could push the Italian blue-chip FTSE MIB index down by 6 percent by early 2017 if the "No" campaign wins, which is its base case scenario.
Shares in UniCredit and Intesa Sanpaolo both fell more than 3 percent, while Banco Popolare fell 4.8 percent. In a sign of more stress, the cost of insuring UniCredit's debt against default hit a high since the end of June when the bank formally announced the exit of former CEO Federico Ghizzoni.
UniCredit's five-year credit default swap UNIC5YEUAM=MG rose to 221.2 basis points on Friday up from 219.8 basis points late on Thursday, meaning it now costs 221,200 euros to insure 10 million euros of UniCredit's debt against default over five years, based on Markit data. As a comparison, Deutsche Bank's five-year CDS DB5YEUAM=MG stood at 218.4 basis points.