A French tax evasion probe is hotting up for UBS: the Swiss bank's dealings with a whistleblower are being examined by a judge. 

Zurich-based UBS' years-long dispute with authorities in France is one of the Swiss bank's largest chunks of regulatory issues still outstanding.

Now, the bank is accused of harassing a whistleblower who brought the case to light ten years ago, according to newswires «AFP» and «Bloomberg», which cite sources

Herd of Whistleblowers

The most recent chapter of the saga centers around Nicolas Forissier, an ex-UBS banker. Forissier isn't the only whistleblower to deliver information to authorities: Olivier Forgues, Thomas Le Forestier and Serge Huss also apparently pitched in.

Former UBS marketing executive Stephanie Gibaud even wrote a book which has prompted a lawsuit by her former employer for defamation.

Vigorous Defense

UBS had to pay 1.3 billion Swiss francs three years ago as a type of corporate bail; the bank may ultimately be fined as much as 6 billion francs, media reports have speculated.

The bank has pledged a vigorous defense – and until now very much followed through on the promise. UBS boss Sergio Ermotti made clear last month that the bank prefers to sweat out the probe instead of making painful concessions to reach a rapid settlement, as has become its habit.