Barclays shares ended trading down 15.5% following the news that the bank had been fined £290m by investigators probing how lending rates were manipulated during the financial crisis.
Barclays was fined £290m ($450m) after an investigation into claims that several banks manipulated the Libor rate at which they lend to each other.
HSBC, RBS, Citigroup and UBS are also under investigation.
Investigators say that Barclays’ traders lied to make the bank look more secure during the financial crisis and, sometimes – worked with traders at other banks – to make a profit.
Shares in other banks to fall include – RBS losing 11.5%, Lloyds down 3.9%, and HSBC, 2.6%.
Barclays has acknowledged that its actions between 2005 and 2009 had fallen “well short of standards”.
LIBOR (London Inter Bank Offered Rate) is the rate at which banks in London lend money to each other for the short-term in a particular currency. A new Libor rate is calculated every morning by financial data firm Thomson Reuters based on interest rates provided by members of the British Bankers Association.