The crash impacted some 600,000 accounts at Ulster Bank, leading to speculation that the bank may have to set aside as much as EUR60 million to fund pay-outs to claimants.

The bank claims that the backlog, caused when a systems upgrade to Royal Bank of Scotland's overnight batch processing went awry, has now been cleared, although it may be weeks yet before customers get a clear view of their financial position.

The bank is understood to be negotiating with the central bank over how much money to set aside. Ulster Bank boss Jim Brown, who has already forsaken his bonus for the year, will not be drawn on the sums involved but admits that the bank expects to pay out "tens of million" of euros in compensation.