Banks in Northern Ireland should use their profits to update "antiquated" IT systems which failed leaving thousands of customers unable to use their accounts, a report from MPs said.
The Northern Ireland Affairs Committee said systems were not fit for purpose as it recommended a major overhaul on the back of banks' return to profitability.
Since 2012, Ulster Bank has suffered two major software glitches. One also affected the parent company Royal Bank of Scotland (RBS) and prevented customers from being able to access their accounts.
The committee said: "It is clear that banks' IT systems are not fit for purpose, and this has led to the totally unacceptable situation of some customers being unable to access their accounts, or experiencing other problems, since 2012.
"With a turnaround in the situations of all Northern Ireland's banks, whereby they have now returned to profit, we believe that some of those profits should be used to update their IT systems, thereby benefiting their customers."
In June 2012 a system failure caused by a botched IT upgrade prevented Nat West, RBS and Ulster Bank customers from being able to access their accounts into late July, with ongoing issues stretching into August.
Then, in December 2013, Ulster Bank customers experienced more payment and account problems, just days after many customers were unable to access online systems or use bank cards for payments, the report said.
There were further problems in April 2014, when some Ulster Bank customers reported that ATM withdrawals had been debited from their accounts twice.
RBS has been fined £56 million by the UK's financial regulators over the IT meltdown in 2012.
The committee said: "The public were badly let down by Ulster Bank, and we believe, therefore, that either Ulster Bank, or the FCA (Financial Conduct Authority), should publish its report into the bank's 'IT glitch' without any further delay."
In a memorandum submitted to the committee by the IBOA bank workers' union, it was stated that: " Northern Ireland may also suffer in terms of the quality of investment in its economic, commercial and social infrastructure.
"Northern Ireland may not rate highly in either strategic or operational priorities - as Ulster Bank's customers will readily testify when a temporary IT glitch for RBS and NatWest customers became an IT meltdown for Ulster Bank - lasting weeks."
Sam Woods, from the Bank of England Prudential Regulation Authority, told the committee early last year that: "T his is a very difficult area, not least because the IT systems are so antiquated.
"Although I feel we are making progress - for instance, the breakdown that RBS had shortly before Christmas did not escalate to the same level of issue partly because of the remediation that has been done following the June 2012 incident - I feel we are, I am afraid, a very long way from being able to sit here with confidence and say, 'UK, including Northern Ireland, banks' IT systems are robust'."
A report entitled Northern Ireland: Banking On Recovery? was published by the committee on Monday.
It said the Northern Ireland economy has shown clear signs of recovery, with many new jobs recently being announced and the banks themselves showing a return to profitability.
But it warned overly-conservative lending by banks in Northern Ireland has discouraged businesses from pursuing opportunities for growth.
It said institutions appeared reluctant to lend to any other than the most financially robust customers.
The First Trust Bank (FTB) and Danske have not participated in the Government's Funding for Lending Scheme, potentially denying further capacity for new business, a report from the parliamentary watchdog said.
Chairman Laurence Robertson said: "From the reckless high-risk attitude of many banks pre-financial crisis, the pendulum appears to have swung too far back in the opposite direction."
Recent statistics show a slight improvement in borrowing by small and medium enterprises last year.
The committee said: "We believe that the more conservative lending criteria has dissuaded many businesses from pursuing opportunities that would require bank financing.
It said some banks have shown relatively little concern for their customers by pursuing plans to close local branches.
"While some of these closures are due to reduced customer activity in branch and greater use of internet banking, it is not always appropriate for rural areas."
It added there was cause for continued concern about the property market and the recent sale of Irish bad loans bank NAMA and Ulster Bank property loan books.
"But there are clear, positive signs of signs of recovery in the economy which the banks need to capitalise on.
"The Northern Ireland Executive should keep a close eye on the relationship between Cerberus, the partial successor to NAMA, and businesses in Northern Ireland."