The Greeks probably knew that a tongue-lashing over the country’s stumbling financial overhaul effort was coming. What they probably did not expect was that beleaguered Spain and Italy, as opposed to economically robust Germany, would take the lead in upbraiding them.

The meeting, on May 6, showed that the disagreements in the euro zone were not just between richer northern countries like Germany and the less wealthy south.

Struggling countries like Spain and Italy fret that any Greek failure on spending cuts might cause investors to conclude that those two countries have no better growth prospects than Greece — even as their own austerity programs cause social and political unrest.

On Monday, the bond market seemed to fulfill Spain and Italy’s worst fears about being lumped in with Greece’s as a poor investment risk and the perception that the cuts meant to ease those countries’ debts will instead mire them deeper in recession.

Ten-year yields for Italian bonds edged up to 4.8 percent on Monday, from 4.7 percent last week. Rates for Spain’s comparable bonds rose to 5.5 percent, up from 5.2 percent. Euro zone unity has always been a challenge to maintain, given the member countries’ contrasting histories and cultures. That it should be crumbling barely a year after European governments agreed to a rescue package underscores the difficulty in translating grand policy ideals into workable achievements.

And that it is Spain and Italy now stressing the necessity of austerity — not Germany or the European Central Bank — is further evidence that bond market investors continue to be the most powerful voice in this debate, Mr. De Grauwe said.

Southern countries, he said, are afraid of contagion from Greece’s woes. “But history shows us that you cannot cut deficits in the midst of a recession.”