Jean-Claude Trichet, ECB president, used his regular interest rate conference to announce rule changes that were more radical than had been expected and will hit financial firms that have developed too great a dependence on cheap funding from the bank.
Mr Trichet announced a series of measures to increase the cost of using asset-backed securities to obtain ECB funds and exclude such deals when the underlying mortgages or other loans are not denominated in euros.
Concerns about potential abuses of the system were first raised earlier this year when it emerged that Macquarie Bank had constructed a deal backed by Australian car loans that could be used at the ECB and Lehman Brothers had created a huge collateralised loan obligation of risky buy-out debt to use at the central bank.