Stephen Hester, chief executive of the Royal Bank of Scotland (RBS), says there is a risk to "turn over rocks and find new things" that are still problems in the banking industry.
After nearly four years on the board of RBS, Mr Hester believes that the "vast majority of things that were wrong at the bank have been discovered and have been changed".
Speaking to the Today programme, he urges not to give up on the banking industry.
"This is an industry that the world needs... we need to reform this industry and change it," he said and admits that banking has become "a bit detached from society" but is now "coming down to earth with a bump".
"A successful business must be built off the back of serving the customers well," he told John Humphrys.
Mr Hester's comments come as the bank announced half yearly losses of £1.5bn and that it will set aside millions of pounds to compensate customers affected by the computer systems failure in June.
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