U.S.-listed shares of UBS dropped 6 percent Tuesday after the company was ordered by tax authorities in Switzerland to provide France with tax information.
The slide also came amid a drop in many European financial stocks. The Stoxx Europe 600 banks index fell nearly 3 percent on Tuesday.
The request relates to UBS account numbers "pertaining to current and former French domiciled clients and is based on data from 2006 and 2008," UBS said in a statement.
The financial services firm also said the legality of the request was "ambiguous" at best, and that "the data and the justification received as part of the request lack the required specificity." The company added it plans to ask the Swiss Federal Administrative Court to look at the request.
The company anticipates other countries making similar requests following the Swiss ruling.
Governments around the world have buckled down on tax evasion, with authorities examining Swiss banks in the U.S., France and Germany.
In 2014, French authorities placed UBS under examination on whether the company helped clients avoid taxes. Judges ordered the bank to provide $1.2 billion in bail.
The company noted that as of January 2017, the automatic exchange of tax-relevant client data between states will take effect in Switzerland, under which all Swiss banks will have to provide data to French and other authorities annually.
UBS's stock has fallen sharply this year, shedding 36 percent of its value.
UBS 2016 Chart