The Royal Bank of Scotland has said the problems at its subsidiary Ulster Bank could continue into next week.
RBS Chairman Philip Hampton apologised to customers for the technical errors that have led to the disruption of account payments of Ulster Bank customers for almost two weeks.
The technical fault has led to a backlog of unprocessed transactions, which will be increased further today when 48,000 monthly social welfare payments are due to be paid to Ulster Bank customers.
The Oireachtas Committee on Finance has called representatives of the Central Bank to appear before it tomorrow and Ulster Bank management to appear before it on Thursday.
The Consumers’ Association of Ireland says it has received thousands of complaints from Ulster Bank customers, who are very frustrated at the poor quality of information they are receiving from the bank.
Chief Executive Dermot Jewell said: "Many, many consumers out there and bank customers were not ready for this. They found themselves on a back foot.
“And now they are struggling to figure out what are they going to do ... It is chaotic for them, because they are completely at a loss."
Meanwhile, Ulster Bank's head of retail banking has said that once technical errors have been resolved, the bank will work towards rebuilding the public's trust "one customer at a time".
Speaking to BBC Radio Ulster, Stephen Cruise said that while the bank is making “progressive improvements”, its recent difficulties were “unprecedented” in the three decades he has worked with Ulster Bank.
He said he was "very sorry" for what had happened.
He assured concerned customers that they will not be left “out of pocket” for expenses incurred as a result of the bank's problems.
Mr Cruise rejected the assertion that the bank had been "economical with the truth" concerning the length of time it has taken to resolve the issue.
He said "the bottom line" was that the problem was "very technical" and that where a timeframe for fixing it has been given, this was done in good faith.