Barclays share price has plunged by 17 per cent after the UK bank was hit by record fines for distorting key interest rates.
The rates concerned play a major role in international financial markets and affect how businesses and consumers borrow money.
Barclays agreed to pay $453m for using underhand tactics, including price-fixing, to rig the markets.
Other British banks also slumped on reports that the scandal was set to engulf HSBC, Lloyds Banking Group and Royal Bank of Scotland.
Laurence Lee reports from London.