A former UBS trader accused of fraud says he wasn't acting as a rogue trader when he lost $2.3 billion.

Kweku Adoboli took the stand for a second day in his trial at London's Southwark Crown Court, telling the jury the losses came after senior traders persuaded him to change from a bearish to a bullish point of view in July 2011.

He testified Monday that he studied the market to "reduce the number of things that are going to be surprises." But he says that "if that is just a calculated gamble, then all investment banking is a calculated gamble."

Prosecutors say Adoboli lied, invented clients and breached safeguards against high-risk trading to make money for the Swiss bank and boost his bonus. He denies the charges.