France's highest court on Wednesday rejected an appeal by Swiss banking giant UBS, ordering it to pay a 1.1-billion-euro ($1.3 billion) security deposit as part of a probe into allegations it helped rich French clients hide money in Switzerland.
The bank said in a statement it was "disappointed" by the ruling against its final appeal, and vowed to take the matter to the European Court of Human Rights.
The bank was ordered to pay the hefty guarantee after being charged with tax fraud in July. It already lost an earlier appeal against the payment in September.
"As we have said before, UBS believes that the basis for calculating the bail amount is exaggerated, speculative and not based on facts," the statement read.
"The matter is still at the stage of a formal investigation and we will continue to defend ourselves vigorously," it added.
UBS's Swiss business is suspected of illegally canvassing French customers and setting up dual accounts to hide the movement of capital into Switzerland.
The charges relate to money kept in accounts in Switzerland between 2004 and 2012. A probe was launched after former UBS employees blew the whistle.
UBS denies the charges.