HSBC says it has been placed under formal criminal investigation by French magistrates over alleged past tax-related offences at its Swiss private bank.
It added that bail of €1 billion has been imposed.
HSBC said it believed the French magistrates' decision was "without legal basis and the bail is unwarranted and excessive".
It planned to appeal and would "defend itself vigorously".
The French claims relate to the conduct of HSBC's Swiss private bank in 2006 and 2007.
HSBC has come under fire over what it knew about some clients' tax affairs.
Details of some 30,000 accounts at HSBC's Geneva-based private bank were leaked to the French authorities by a whistleblower, Herve Falciani, in 2007.
Information about 3600 UK account holders were passed to HMRC.