Bad behaviour that has cost British banks £38.5 billion in fines and compensation over the past 15 years will take a generation to fix, an independent think tank has said.
UK banks have been hit by scandals ranging from the attempted manipulation of foreign exchange and benchmark interest rates to the mis-selling of loan insurance.
The report into the culture of British retail banking was carried out by think tank New City Agenda and Cass Business School.
It found that an aggressive sales culture took hold over two decades, with some branch staff receiving cash bonuses, iPods or even tickets to the Wimbledon tennis tournament for hitting sales targets.
"A toxic culture which was decades in the making will take a generation to turn around," said David Davis, chairman of New City Agenda.
"At this critical juncture, Britain's biggest banks cannot afford to let the better treatment of customers become a second-order priority," he added.
The report said the mis-selling of payment protection insurance (PPI) alone cost banks at least £27 billion in Britain's costliest consumer scandal.
The high-margin products were meant to cover repayments if customers fell ill or were out of work but were often sold to people who did not need them or would be ineligible to claim.
The biggest sum set aside by a bank for PPI compensation is the £11.3 billion at Lloyds Banking, followed by Barclays (£5 billion), RBS (£3.3 billion) and HSBC (£2.5 billion).
New City Agenda noted that banks had received 20.8 million complaints since the 2007/09 financial crisis, during which time there was a fivefold increase in cases going to the financial ombudsman, which settles disputes when banks and customers fail to reach agreement.
It recommended that the new Banking Standards Review Council should talk to branch staff to check they are not under pressure to sell and should report annually to parliament's Treasury Committee, which oversees the work of the finance ministry.
"The need for culture change has been recognised, but it has to be transmitted all the way from the top to the bottom of these huge organisations," said John McFall, a director of New City Agenda and former Treasury Committee chairman.