LONDON (AP) — French authorities have placed HSBC under formal criminal investigation over alleged tax fraud by its Swiss private bank. The bank said Thursday the claim was "without legal basis."

The London-based bank said French authorities have imposed bail of 1 billion euros ($1.1 billion) while they investigate alleged wrongdoing in 2006-2007.

HSBC'S Swiss bank is under investigation in several countries after leaked documents suggested it hid millions of dollars as it helped wealthy people around the world dodge taxes.

A former HSBC employee, Herve Falciani, gave the data to French tax authorities in 2008. France shared it with other governments and launched investigations.

A spokesman for the French financial prosecutor's office, Franck Charon, said the London-based bank was placed under investigation on Wednesday in the long-running French probe for tax fraud.

He confirmed the 1 billion-euro amount is meant to guarantee the bank would be represented should the case go to trial and would pay any fines and damages.

In a statement Thursday, HSBC said "the French magistrates' decision is without legal basis and the bail is unwarranted and excessive." It said it would defend itself "vigorously" in any legal proceedings.