Speaking to the Treasury Select Committee in parliament, Woods described the outage suffered by customers of TSB as an enormous inconvenience and a "very severe operational failing".

This was why the Bank was investigating it jointly with the Financial Conduct Authority, and that investigation was on-going, Woods said. TSB's owner, Spanish bank Sabadell, has estimated the outage has cost it at least 320 million euros.

Woods said he had required TSB to set aside capital to cover an "unspecified" possibility of the IT project going wrong.

"Now that it has gone wrong and proved to be very expensive, it's a very good thing that we have that capital requirement in place," Woods said.

(Reporting by Huw Jones; Editing by Peter Graff)