Citigroup today reportedly said it was concerned over a "perception of potential insider trading" when it dealt shares in a company targeted for acquisition by one of its clients, as it opened its defence in a landmark case marking the first time insider trading charges have been brought against a bank.

Citigroup's head of investment banking in Australia, Stephen Roberts, said he had sought reassurance from the bank's head of compliance, Peter Monaci, and been told that all the correct controls were in place.