Image by U-g-g-B-o-y-(-Photograph-World-Sense-) via Flickr
Brian Coulton, the agency's head of sovereign ratings, said German members of the ECB appeared to be blocking the sort of muscular intervention in southern European bond markets needed to restore the shattered confidence of investors.
"There has been an unwillingness to follow through, and markets are going to want to see the ECB's money. It will require hundreds of billions in my opinion," he told a global banking conference.
The ECB agreed to start buying Greek, Portuguese, and Irish bonds in April to help buttress the EU's `shock and awe' package, known as the European Financial Stability Facility. Total purchases so far have been €47bn (£39bn).
It has focused its firepower on Greece, mopping up some €25bn of government bonds. This has prevented a collapse of the Greek debt market but at the high political price of letting banks and funds dump their holdings onto the EU taxpayer.
ECB council member Jose Manuel Gonzalez-Paramo said it was "not entirely correct" to assume that the ECB was the sole buyer of the debt. "We will continue buying bonds until the situation has stabilized," he said.
The Bundesbank is reportedly irked that French banks have led the rush to the exits while German banks have stuck by a gentleman's agreement to keep their Greek assets. The ECB's council insists that it has "sterilized" all purchases, offering no net stimulus. In effect, the ECB has done little to offset severe fiscal tightening by some eurozone states, and as the M3 money supply contracts.