FRANKFURT — Citizens from Prague to Paris to Amsterdam have made it abundantly clear the last few days that they are tired of the economic austerity forced on them by the euro zone debt crisis.


But as the budget-cutting pain of reduced government benefits and social services brings protesters to the streets and drives support for nationalist or far-left parties, it is not clear what the economic alternative might be. Rejecting austerity budgets in favor of more government spending will not automatically ensure economic growth, many economists say.


“The last thing these economies need is a debt-financed stimulus program,” said Jörg Krämer, the chief economist of Commerzbank in Frankfurt.


Governments in countries like Spain are having enough trouble financing their existing debt, much less coming up with money for stimulus spending. Germany, the only large country in the euro zone with budgetary room to increase its deficit by spending more, is not willing to. (And neither was the Netherlands, at least until its government collapsed Monday over a dispute that essentially involves the austerity vs. growth debate.)


Financial markets were down deeply and broadly in Europe Monday, on concerns over the backlash to austerity, and the sell-off carried over to the United States markets.


As more European countries teeter on the edge of recession or slip into one — Spain, on Monday, was the latest to slide — even the policy-making elite has begun to question whether Germany and the European Central Bank have gone too far in insisting that fiscal discipline is a prerequisite to growth.


Euro zone unity is under strain as other Europeans resent what they perceive as Germany’s holier-than-thou attitude in insisting that all countries in the euro currency union keep their promises to reduce government budget deficits to 3 percent or less of gross domestic product. Germany’s government deficit was a modest 1 percent of gross domestic product at the end of 2011.


“A global, undifferentiated rush to austerity will ultimately prove self-defeating,” Christine Lagarde, the president of the International Monetary Fund, said at the fund’s spring meeting in Washington on Saturday.


But Ms. Lagarde also acknowledged the quandary facing European leaders. Most of them simply do not have the resources to pay for public works projects or social programs that would ease the pain of rising unemployment and declining wages.


At the monetary fund meeting, Treasury Secretary Timothy F. Geithner continued his call for Europe to at least temporarily set aside budget cutting and engage in the sort of government spending stimulus that the Obama administration prescribed for the American economy in 2009.


(The United States, to the extent that it can continue getting away with its gaping budget deficit, relies on the world’s seemingly insatiable appetite for the Treasury bonds that finance the American debt and deficit.)


The central, existential issue facing the euro zone is how to escape a vicious cycle. Budget cuts drag down growth and push up unemployment. Then, revenue falls as fewer people pay taxes — forcing even more austerity. Economic growth seems absent from the equation.


On Monday there was fresh evidence of the poor state of the euro zone economy. Official data confirmed that Spain is in recession, after economic output fell 0.4 percent in the first three months of the year. Spain joins other European countries now in recession, including Italy, Belgium, the Netherlands and, outside the euro zone, the Czech Republic. Even Germany may have fallen into recession in the first quarter, economists say, though official data is not out yet.


Meanwhile, a survey of European purchasing managers released by the research firm Markit on Monday showed an unexpected decline in confidence during April.


Signs of popular frustration are multiplying. In France, voters on Sunday gave the Socialist candidate, François Hollande, the most votes in the first round of presidential elections, after he promised to delay balancing the budget and instead hire more teachers and police officers and raise subsidies for industry.


President Nicolas Sarkozy’s tight-budget policies in response to the euro zone crisis are one reason he is at risk of being voted out of office.


In Prague, an estimated 90,000 Czechs took to the streets on Saturday to demonstrate their lack of faith in a government that has cut the budget while raising taxes, and that also faces accusations of corruption.


Even the prudent Dutch face a political crisis as they try to agree on a government budget. The far-right Freedom Party of Geert Wilders walked out of budget talks rather than support more cuts needed to bring the deficit back in line with European Union rules.


These signs of unrest, though, do not seem to be mellowing Germany’s insistence on strict austerity. Jens Weidmann, president of the Bundesbank, the German central bank, argued Monday that the core problem in the euro zone was a lack of faith in the soundness of governments’ fiscal health.


The only solution, Mr. Weidmann said at the Economic Club of New York, is to put public finances in order.


“There is little alternative,” said Mr. Weidmann, who is an influential voice on the governing council of the European Central Bank. “In the end, you cannot borrow your way out of debt; cut your way out is the only promising approach.”


Mr. Weidmann’s views are widely shared in Germany. But Germany is becoming isolated in Europe as an increasing number of economists and policy makers argue that euro zone countries could do more to offset the social effects of austerity on ordinary Europeans, which include a surge in suicides.