Rudolf Elmer handed over two discs of data to Wikileaks, which could contain evidence of tax evasion and criminal activity committed by prominent people, said reports on the BBC. Elmer will go on trial for breaking bank secrecy laws.
In a statement, the bank told the BBC: "Evidently disgruntled and frustrated about unfulfilled career aspirations, Elmer exhibited behaviour that was detrimental and unacceptable for the bank, which led to termination of the employment relationship."
US authorities are reportedly urging government agencies to set up programmes to identify disgruntled employees who might leak sensitive information. The move comes after whistle-blowing website Wikileaks published thousands of leaked US diplomatic cables.
Twitter was recently issued with a subpoena by the US government to release the personal details of people connected to Wikileaks, including Julian Assange.
The bank account data is expected to appear on the Wikileaks website once the information has been vetted.
This story was first published by Computer Weekly