The fraud took place between January and September this year, and Adoboli filed false accounts between October 2008 and December 2009, and from January to September 2011, according to the charges.

Prosecutors say Mr Adoboli "dishonestly abused that position intending thereby to make a gain for yourself, causing losses to UBS or to expose UBS to risk of loss".

He has been remanded in custody until a committal hearing on 22 September. UBS is expected to provide more details of Adoboli's trading by Monday morning.

The 31-year-old worked for UBS's global synthetic equities division, buying and selling exchange traded funds, which track different types of stocks or commodities such as precious metals.

The BBC reports that Mr Adoboli worked in the back office before becoming a trader, which may explain how he managed to keep his trading secret.

The Financial Services Authority (FSA), the City regulator, is investigating why the Swiss bank did not identify the trades.

BBC