The ECB remains at the centre of a fierce political tug-of-war, as the central bank, backed by Germany, continues to resist calls from France and Italy as well as from the US, Britain and Russia to calm the euro zone debt crisis by being more forceful in its bond buying.
Weekly figures from the central bank showed it bought 635 million euros worth of bonds last week, well below the 3.7 billion of the previous week and further evidence of its reluctance to buy down the borrowing costs of troubled euro zone members.
It takes the total the ECB has spent since starting the controversial programme in May 2010 to 207.5 billion.(for full details click ). There has been no clear change in the ECB's bond buying tactics since Mario Draghi took over as the bank's president from Jean-Claude Trichet last month.
Last week the Italian dashed hopes the bank was gearing up to get more aggressive with its purchases, saying his comments the week before that if leaders agreed to more shared spending and debt rules "further elements might follow", had been wrongly read as code for more bond buys.
The ECB has capped the maximum purchase of euro zone sovereign bonds at 20 billion euros a week for now and is not considering bigger action in response to the EU summit decision to create a fiscal union, ECB sources told Reuters on Friday.
The ECB and the 17 euro zone national central banks are buying the bonds under what it calls its Securities Markets Programme (SMP). It buys the bonds from banks and other investors on the secondary market as European laws forbid it from buying direct from the governments themselves.
It reactivated the programme back in August after a four-month break when Italy and Spain, two of the euro zone's biggest economies, began to be dragged into the eye of the euro zone debt crisis. Since then it has spent over 130 billion euros, averaging at just over 8 billion euros a week.
Critics argue the purchases tread dangerously close to the ultimate ECB-taboo of financing euro zone governments.
Juergen Stark, who is about to quit the bank over what sources say is his opposition to the SMP, said in an interview published on Monday that it was a matter of debate whether the buying had already overstepped the line of what the ECB can do.
The purchases are reported by the bank every week but take two to three days to settle, meaning that when it is buying, the figures do not necessarily give a full picture.
Also problematic is that it does not give a country-by-country breakdown of its purchases. However, analysts and traders estimate it has bought around 45 billion euros of Greek debt in total and has concentrated largely on Italian and Spanish debt since the August restart.
As usual the ECB will hold a so-called 'sterilisation' operation on Tuesday to neutralise the inflationary pressure the bond buys create. It does so by taking deposits from banks that when combined add up to the same amount it has spent on bonds.
Focus on the operation has intensified recently after the ECB failed to fully offset the purchases late last month, raising questions whether the total is now so large that neutralising the purchases may become a more regular problem