LONDON — Europe may have sidestepped its latest catastrophe, at least for the moment, by hammering out a €100 billion bailout plan for Spain’s failing banks over the weekend.


But the intervention will do little to address the problem that continues to plague the Continent’s increasingly vulnerable financial institutions. Namely: a longstanding addiction to the borrowed money that provides the day-to-day financing that they need to survive.


It is a weakness that afflicts many euro zone banking systems — most notably that of Italy, whose fragile economy is even bigger than Spain’s and whose banks also rely heavily on borrowed money to get by.


In Spain’s case, the flight of foreign money for safer harbors, combined with a portfolio of real estate loans that has deteriorated along with the Spanish economy, led to the collapse of Bankia, the mortgage lender whose failure set off the country’s current banking fiasco.


Europe hopes that this latest bailout — money that will be distributed to Spain’s weakest banks via the government in the form of loans, adding to their long-term debt — can resolve the problem. But investors and analysts worry that highly indebted banks in other weak countries like Italy might face similar difficulties in the months ahead.


Last month, the ratings agency Moody’s downgraded the credit standing of 26 Italian banks, including two of the largest ones, Unicredit and Intesa Sanpaolo. Moody’s warned that Italy’s most recent economic slump was creating more failed loans and making it very difficult for banks to replenish their coffers through short-term borrowing.


Because they have suffered no epic real estate bust, Italian banks have long been seen as healthier than their bailed-out counterparts in Ireland and Spain. And bankers in Italy have been quick to argue that Italian banks should not be compared to those in Spain.


But as economic activity throughout the region comes to a near halt, especially in perpetually growth-challenged Italy, the worry is that bad loans and a possible flight of deposits from the country will be a new threat to banks that already are barely getting by on thin cushions of capital.


And Italian banks cannot avoid the stigma of their government’s own staggering debt load. Italy’s national debt is 120 percent of its gross domestic product, second only to Greece among euro zone countries by that dubious distinction.


Also hanging over European banks are the losses that would hit them if Greece were to leave the euro currency union, throwing most of their euro- denominated Greek loans into default. Banks in France and Germany would be hurt the most, as they have been longstanding lenders to Greece. In a recent analysis, Eric Dor, an expert on international finance at the Iéseg School of Management in Lille, France, calculates that French and German banks would be out €20 billion and €4.5 billion, respectively.


The French bank Crédit Agricole, for example, via its Greek subsidiary, has about €23 billion in Greek loans on its books. If Greece were to leave the euro, the losses could exceed €6 billion, analysts estimate.


Because it was the financial excesses of banks in Ireland, and now Spain, that eventually forced those countries to seek bailouts, finding a Europewide solution to overseeing financial institutions has become a pressing priority for the euro zone’s leadership. Otherwise, Europe will be able to address the weaknesses of member country banks only when the time comes to rescue them.


But as the president of the International Monetary Fund, Christine Lagarde, said in a speech in New York on Friday, there is little time to waste in this regard.


“European banks are at the epicenter of our current worries and naturally should be the priority for repair,” she said.


Ms. Lagarde, who from her earliest days at the fund has focused on banking problems in Europe, left little doubt about how the issue should be addressed. “Let me be clear,” she said in her speech. “The heart of European bank repair lies in Europe. That means more Europe, not less. Less Europe will be bad for the Continent and bad for the world. So, policy makers in Europe need to take further action now to put the monetary union on a sounder footing.”