Bank account holders in the UK have fallen victim to a scam operated from a call centre in India.
Money was taken from the accounts of a "small number" of HSBC customers based in the UK, the bank said.
The banking giant said it had begun legal action against one of its employees at its Bangalore call centre who it believed was supplying data to fraudsters.
A spokesman for the bank said: "HSBC will be assisting the Indian police with their investigation.
"We intend to pursue a conviction as aggressively as possible."
The amount of money taken is believed to be around #233,000, but the bank could not confirm that figure.
He said the bank had contacted all the customers affected and any losses would be reimbursed to the victims by HSBC.
He added the fraud had been detected by internal systems at the call centre, in operation since 2002.
Following the news of the alleged breach of security, the vice president of NASSCOM - the trade body for the Indian IT and services sector -Sunil Mehta said the organisation would work with legal authorities in the UK and India to ensure any criminal breaches in security were promptly prosecuted.
"Any case of theft or a breach of a customer's confidentiality must be treated extremely seriously," he said.