The bank issued an unusually strongly worded condemnation of the bail order, issued at a Paris hearing earlier in the day, alleging political undertones as a French investigation into how it dealt with its wealthy clients there widened.
"We were notified today at a convocation hearing in Paris of an unprecedented and unwarranted amount of bail amounting to 1.1 billion euros in the ongoing investigation of UBS AG's French cross-border case," the Zurich-based bank said in an emailed statement following a inquiry from Reuters on Wednesday.
"We consider both the legal basis for the bail amount and the method of calculation to be deeply flawed and will appeal ... It is not acceptable to us that this has become a highly politicized process."
"We will continue to defend our case strongly," UBS said.
It was not immediately clear if any individuals at the bank were named as the subjects of the bail order.
Last year, a French prosecutor put the UBS head office and its subsidiary in France under formal investigation on related charges of illegal sales practices and complicity in illegal sales practices, respectively.
The alleged sales practices in question involved seeking out wealthy customers in France who would be interested in opening bank accounts inaccessible to French tax authorities.
Three former and current executives with UBS' French subsidiary were also individually placed under investigation, a spokesman at the subsidiary said on Wednesday.
"In the course of the last few years, we have done everything we can to bring this matter to a close. We have also taken significant and broad steps to ensure tax compliance of our clients and will continue to do so," UBS said.
French judicial authorities probing UBS over the allegations visited the bank's Paris headquarters in November.
(Reporting by Chine Labbe, Katharina Bart, and Nick Vinocur; Editing by David Holmes, David Evans and Hugh Lawson)