TSB boss Paul Pester has stepped down from the beleaguered bank after further IT problems saw customers again locked out of their accounts.
It is the latest a string of technology failures that began in April with a botched migration to a new system that saw up to 1.9 million customers denied access to online banking.
The chief executive's seven-year tenure ended with immediate effect on Tuesday morning.
TSB's non-executive chairman, Richard Meddings, will become executive chairman and start the search for a new CEO.
The news came shortly after hundreds of TSB customers posted on social media on Monday that they were experiencing issues including “duplicate transactions”.
Mr Meddings said: “Although there is more to do to achieve full stability for customers, the bank's IT systems and services are much improved since the IT migration.
“Paul and the board have therefore agreed that this is the right time to appoint a new chief executive for TSB.”
MPs on the Treasury Select Committee have heavily criticised Mr Pester for his handling of the bank's technology problems.
In June, committee chair Nicky Morgan accused Mr Pester of delivering “complacent and misleading” messages to the public and MPs and said the bank’s board should give “serious consideration as to whether his position was sustainable”.
Mr Meddings said on Tuesday: “Together with the executive committee, we have three immediate priorities: to complete the work of putting things right for customers; to enable the bank to achieve full functionality - including the availability of all product services and launch of a leading business banking offer; and appointing a chief executive for the next chapter of TSB.”
