The ECB terminated its Securities Markets Programme (SMP) last September to replace it with a new but yet-to-be used plan dubbed Outright Monetary Transactions (OMT).
But because the ECB has said it will keep the bonds it acquired under the SMP programme until maturity, it will be years before the programme ceases to exist.
The ECB revealed in February for the first time the contents of its SMP portfolio, showing that it had 99 billion euros of Italian bonds, 44 billion of Spanish, 31 billion of Greek, 22 billion of Portuguese and 14 billion euros of Irish government debt at the end of last year.
The ECB will take an amount equivalent to the current SMP holdings as weekly deposits from banks on Tuesday to counterbalance the buys and neutralise any threat of them fuelling inflation.