MPs have launched an inquiry into the "astonishing" number of IT failures at banks following a string of recent meltdowns.
The Treasury select committee will focus on the causes of the problems, how consumers lose out, and whether regulators are properly equipped to hold firms to account.
Millions of customers have been hit by problems over the past year including a disastrous IT migration at TSB, online banking failures at Barclays and the Royal Bank of Scotland, and Visa's card network crashing.
It comes at a time when bank branch closures mean account holders are increasingly reliant on being able to access their money online.
MPs say they will examine the ability of financial services companies to guard against service disruptions and to put them right if they do happen.
Nicky Morgan, chair of the committee, said: "The number of IT failures at banks and other financial institutions in recent years is astonishing.
"Millions of customers have been affected by the uncertainty and disruption caused by failures of banking IT systems.
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"Measly apologies and hollow words from financial services institutions will not suffice when customers aren't able to access their own money and face delays in paying bills.
"As bank branches close and customers are ushered towards online services, the availability of those services is vital."