Matthew Elderfield has said that if Ireland had had the supervisors and regime for winding up banks that it has now, it would have known Anglo Irish Bank was insolvent on the night of the bank guarantee.
The Central Bank deputy governor also told the Public Accounts Committee that it would have been evident that Irish Nationwide was in trouble "on that fateful night".
The regulator also said the regime to deal with white collar crime involving individuals is not working sufficiently well and he advocated a review of the system by a retired judge or former attorney general.
He told the committee that provisions which could be introduced include the disqualification of directors of failed banks.
When asked if he thought the banks would need a further bailout, Mr Elderfield said that the banks have plenty of capital right now but in the future they are going to need more.
He said the question is how soon the banks will they need that. He said the banks currently have a buffer of capital but that will erode over time.
Mr Elderfield that international banking rules such as the Basel 3 directive mean that the banks will be required to have tougher capital over time. He said the new rules will be phased in over five years from 2014 at 20% every year.
The regulator also warned of more losses coming from the banks, adding that the Central Bank will get Blackrock International to carry out another independent stress test on the banks.
But there are some positives in the banks, Mr Elderfield stated as arrears remain inside stress test levels, house prices have stabilised, and assets have been sold.
He added that on the negative side arrears are still trickling up, the economy is still weak and the insolvency is still the big unknown.
When asked why he was leaving Ireland, Mr Elderfield told the committee it was a personal decision.
He said he and his wife had gone back to London last summer for the Olympics and realised how much they missed living there. He said that Dublin was a great city and he had enjoyed his time there but now wanted to go home.
When asked if his leaving before the end of his contract was an indication of disappointment, Mr Elderfield said it was not.
He said he was confident that a strong legislative framework was in place and that the Irish financial system was on the right track.