Wolfgang Kuhn, Aberdeen Asset Management's head of pan-European credit, said: "The opinion criticises the German court for daring to refer the case the way it did and seems to say that it can't be up to national courts to judge what goes on at a European level.
"The opinion removes another inconvenient obstacle to [ECB president Mario] Draghi's big quantitative easing gamble, which will now almost certainly be announced next week. But the voices that see both OMT and QE as a blatant breach of EU treaty law will only grow more shrill."