(Bloomberg) -- The European Commission threatened twice in a weekend to sue Germany over a ruling by the country’s constitutional court challenging the European Central Bank’s monetary authority, raising the prospect of an institutional showdown on the continent amid the deepest recession in a century.

“The final word on EU law is always spoken in Luxembourg. Nowhere else,” Commission President Ursula von der Leyen said in a statement on Sunday, referring to the headquarters of the European Court of Justice. She also threatened a lawsuit, after Germany’s constitutional judges gave the ECB a three-month ultimatum to fix alleged flaws in its quantitative easing policy.

The landmark May 5 German court decision risks opening a legal can of worms, as it challenged the supremacy of European Union judges, whose rulings are binding across the 27-nation bloc. The court accused its EU counterpart in Luxembourg of overstepping its powers when it backed the ECB’s monetary policy.

That poses the risk of other nations starting to doubt the authority of the EU Court of Justice, an issue that may eventually threaten the future of the common currency, according to Wolfgang Schaeuble, Germany’s former finance minister.

“EU law has primacy over national law,” von der Leyen said in her Sunday statement. In a letter to EU lawmaker Sven Giegold published on Saturday, the head of the EU executive arm said the German court ruling is being analyzed and an infringement process against Germany is possible, a threat she reiterated on Sunday.

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