"We're facing maximum tension. The situation is unsustainable over time," said the country's finance minister Luis de Guindos.
Yields on 10-year Spanish bonds yields punched to almost 7pc, above levels that triggered ECB intervention to back stop Spain last November.
"The ECB needs to intervene very quickly or it is game over," said Nicholas Spiro from Spiro Asset Management.
"There is a whiff of capitulation in the air."
The
dramatic escalation comes just days after the eurozone agreed a €100bn rescue package for the Spanish state to recapitalise its crippled banks.
"It is very worrying. Markets are behaving as if the eurozone is heading for break-up," said Jens Sondergaard from the Japanese bank Nomura.
France's industry minister Arnaud Montebourg said the markets were flying out of control because the ECB was failing to take charge. "We need an ECB that does its job," he said.
In an astonishing outburst for a French minister, he lashed out at German Chancellor Angela Merkel and the "German right" for driving much of Europe into slump. "Certain European leaders, led by Mrs Merkel, are fixated by blind ideology."
Spain is caught in a vicious downward spiral as the property crash accelerates, further undermining the banks and state finances. This in turn is drawing Italy into the fire and threatens to overwhelm the EU's rescue machinery.
"We must have a real circuit breaker," said Sondergaard. "The question is whether the ECB will now blink and go down the route of quantitative easing (QE)".
He said the ECB should slash interest rates by half a point to 0.5pc and "pre-commit" to half a trillion euros of QE over coming months, blanketing the Spanish and Italian bond markets.
Nomura said the ECB must act with overwhelming force rather than engaging in piecemeal bond purchases that fail to restore confidence and have the toxic side-effects of pushing existing bondholders down the credit ladder -- the dreaded effect of "subordination".
"The eurozone has the wrong policy mix across the board. Fiscal policy is too tight; monetary policy is too tight; and the tough regulation of the banks is coming at the wrong time.
Together it is all pushing the eurozone to breaking point," he said.
Spanish premier Mariano Rajoy said in a private letter to EU leaders last week that the ECB is the only body with firepower and nimbleness able to contain the crisis at this point.
The pleas have so far fallen on deaf ears in Frankfurt where ECB hawks insist that any such intervention to help EMU's struggling debtors would reduce the pressure for root-and-branch reforms.
The bank said in its June report on Thursday that Spain must make further draconian cuts to meet its deficit target of 3pc of GDP next year. It enraged monetarists by denying yet again that the eurozone faces a serious monetary slowdown or "an abrupt and disorderly adjustment" for banks -- or a credit crunch in layman's language.