The tax affairs of more than 4,000 Britons with an HSBC bank account in Jersey are under scrutiny after their details were leaked to HM Revenue & Customs.
The list, which was passed to authorities this week by a whistleblower, reportedly includes the names of serious criminals.
It will raise further questions about HSBC's procedures at a time when the group is facing fines of about 1.5 billion US dollars (£938 million) in the United States for breaching money laundering rules.
Banks are required to report any suspicious activity that could suggest money laundering, although the responsibility for paying tax lies with the individual.
According to The Daily Telegraph, the list identifies the names, addresses and account balances of 4,388 UK people holding £699 million in offshore bank accounts at HSBC Jersey. In total, there are 8,474 account holders, including 602 addresses from Israel and 527 in France.
The list will now be used by HMRC to identify whether any of the Jersey accounts were used to avoid paying taxes.
HMRC said: "We can confirm we have received the data and we are studying it. We receive information from a very wide range of sources which we use to ensure the tax rules are being respected.
"Clamping down on those who try to cheat the system through evading taxes and over-claiming benefits is a top priority for us, and we value the information we receive from the public and business community."
HSBC said: "We are investigating the reports of an alleged loss of certain client data in Jersey as a matter of urgency.
"We have not been notified of any investigation in relation to this matter by HMRC or any other authority but, should we receive notification, we will co-operate fully with the authorities. HSBC remains fully committed to adoption of the highest global standards including the procedures for the acceptance of clients."