The central bank chief, Jens Weidmann, told Der Spiegel news weekly that the bank's recent moves of setting interest rates at record lows while pumping liquidity into the financial system set a risky precedent.
The package of measures marks "a fundamental change of course and a decisive change for the ECB's monetary policy", he said.
"Whatever you want to say about the content of the decisions, the majority of the ECB Council is saying it is ready to go very far with monetary policy and break new ground."
He said the policy went beyond encouraging banks to make private loans and amounted to pumping money directly into the real economy.
He added that plans announced this month by the ECB to launch an asset-backed securities (ABS) purchase programme could, "depending on how it is set up", eliminate "risk to banks at the expense of taxpayers".
Weidmann said if the bank pressed ahead with the programme it should buy low-risk securities, although he questioned whether there were enough on the
market to meet the volume the ECB has targeted.
In a bid to prevent deflation, the ECB this month cut its interest rates to new all-time lows and unveiled plans for an ABS purchase scheme to help
kick-start credit in the eurozone.
Asset-backed securities are bundles of individual loans such as mortgages, auto credit and credit-card debt that are sold on to investors, allowing banks to share the risk of default and encouraging them to offer more credit.
Some ECB watchers believe the ABS scheme is the first step towards much broader quantitative easing, where the central bank would buy up sovereign bonds on a large scale to inject cash into the economy.