MPs have condemned the level of IT failures at banks, warning that financial levies on firms and more regulation may be needed.
A Treasury Committee report said the frequency of online banking crashes and customer disruption was "unacceptable".
The report, published on Monday, said with bank branches and cash machines closing, there was greater urgency to ensure online banking worked.
Customers are being left "cashless and cut off", the report said. Firms could do much more to ensure their IT systems were resilient and to resolve complaints and compensation more quickly.
The MPs suggest the three major regulators - Financial Conduct Authority, Prudential Regulation Authority, Bank of England - do not have the staff and experience to deal with the growing number of computer failures.
An increase in the financial levies on banks may be needed to ensure that the regulators are adequately funded and resourced , the report says.
MPs are also worried about the increase use of third-party providers of cloud services for computing power and data storage.
"The consequences of a major operational incident at a large cloud service provider, such as Microsoft, Google or Amazon, could be significant," the report said. "There is, therefore, a considerable case for the regulation of these cloud service providers to ensure high standards of operational resilience."
Cloud services "stood out as such a source of systemic risk" for the financial system, the MPs said.
Steve Baker, the Treasury Committee's lead member on the inquiry, said: "The number of IT failures that have occurred in the financial services sector, including TSB, Visa and Barclays, and the harm caused to consumers is unacceptable.
"The committee, therefore, launched this inquiry to look 'under the bonnet' at what's causing the proliferation of such incidents, and what the regulators can do to prevent and mitigate their impacts."
Mr Baker added: "For too long, financial institutions issue hollow words after their systems have failed, which is of no help to customers left cashless and cut off."
The MPs also said there is a "concerning" lack of consistent and accurate recording of data on IT incidents.
If future incidents occur without sanction, Parliament should consider whether the regulators' enforcement powers are fit for purpose, the report said.
TSB suffered a high-profile IT failure last year which left customers unable to access their accounts, following the introduction of a new system.
Up to 1.9 million people lost access to online banking services.
The MPs said regulators must provide them with the outcome of their investigation into the TSB IT failure as soon as possible.
Mr Baker said: "For too long, we have waited for a comprehensive account of what happened during the TSB IT failure. Our inquiry into service disruption at TSB remains open."
Stephen Jones, chief executive of UK Finance, the trade body for the financial services sector, said the industry was investing billions of pounds to ensure its systems are robust and secure.
"When incidents do occur, firms work around the clock to minimise disruption and get services back up and running as quickly as possible," he said.
"The industry conducts sector-wide exercises with regulators to ensure it is prepared to respond effectively to any major disruptions or events as part of its continued commitment to maintaining the resilience of the financial system."
He said UK Finance is working to improve co-ordination with regulators, but it was important to "avoid overlapped or rushed mandatory change programmes that impact firms' ability to protect their customers".