ECB Executive Board member Sabine Lautenschlaeger said on Saturday she saw little room for further easing of monetary policy despite a further fall in euro zone inflation.
"According to the current situation, the threshold as I see it for taking further action is very high, particularly for large-scale purchasing programmes," she said in Berlin, speaking five days ahead of the ECB's next Monetary Policy Committee meeting.
Innovation in monetary policy was not a taboo, but must also not be an "end in itself", she added.
The ECB has cut interest rates to practically zero and is readying more buying programmes that could include government bonds - known as quantitative easing - to ward off the threat of deflation in the euro zone.
Vice President Vitor Constancio said this week the ECB could make a decision on government bond-buying in the first quarter if the economy did not improve.
The purchase of government bonds would be viewed extremely critically in Germany.
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