UBS has said that the estimated total losses to its firm from unauthorised trading now stand at £1.5bn, up from £1.3bn.

The bank confirmed that the trades had been made by a trader working in the global synthetic equity business.

The trades were made on the S&P 500, DAX and EuroStoxx index futures over the last three months.

A 31-year-old man was arrested by City of London Police on 15 September and has since been charged with fraud and false accounting.

He has been remanded in custody until a committal hearing on 22 September.

The Financial Services Authority and the Swiss Financial Market Supervisory Authority are launching an investigation into the unauthorised trading and how the activity remained undetected

It will also assess the overall strength of UBS’s controls to prevent unauthorised or fraudulent trading.

UBS’s board has also set up a committee to conduct an independent investigation led by David Sidwell, former chief financial officer at Morgan Stanley.