WASHINGTON (MarketWatch) — A decision by a new Greek government to leave the eurozone would set off devastating turmoil in financial markets even worse than the collapse of Lehman Brothers in 2008, a leading international economist warned Saturday.

A Greek exit would likely spark runs on Greek banks and the country’s stock market and end with the imposition of severe capital controls, said Barry Eichengreen, an economic historian at the University of California at Berkeley. He spoke as part of a panel discussion on the euro EURUSD, -0.06% crisis at the American Economic Association’s annual meeting.

The exit would also spill into other countries as investors speculate about which might be next to leave the currency union, he said.

“In the short run, it would be Lehman Brothers squared,” Eichengreen warned.

He predicted that European politicians would “swallow hard once again” and make the compromises necessary to keep Greece in the currency union.

“While holding the eurozone together will be costly and difficult and painful for the politicians, breaking it up will be even more costly and more difficult,” he said.

In general, the panel, consisting of four prominent American economists, was pessimistic about the outlook for the single-currency project.

Jeffrey Frankel, an economics professor at Harvard University, said that global investors “have piled back into” European markets over the last years as the crisis ebbed.

Now, there will likely be a repeat of the periods of market turmoil in the region and spreads between sovereign European bonds could widen sharply.

Kenneth Rogoff, a former chief economist at the International Monetary Fund and a Harvard professor, said the euro “is a historic disaster.”

“It doesn’t mean it is easy to break up,” he said.

Martin Feldstein, a longtime critic of the euro project, said all the attempts to return Europe to healthy growth have failed.

“I think there may be no way to end to euro crisis,” Feldstein said.

The options being discussed to stem the crisis, including launch of full scale quantitative easing by the European Central Bank, “are in my judgment not likely to be any more successful,” Feldstein said.

The best way to ensure the euro’s survival would be for each individual eurozone member state to enact its own tax policies to spur demand, including cutting the value-added tax for the next five years to increase consumer spending, Feldstein said.