Shares in UBS, Credit Suisse Group and Julius Baer Group fell this week after Germany threatened to buy stolen details of an unnamed bank's customer accounts as part of its battle against tax evasion. A successful Italian tax amnesty at the end of last year and the prospect of new amnesties in Germany and Belgium have added to fears of a renewed political assault on the industry. But the gloom looks overdone.

Germany's threats are legally dubious and are more likely a ruse to frighten Swiss bank account holders into declaring hidden assets than a serious plan to reward criminals. It highlights the lengths cash-strapped governments will consider to recover lost revenue. Switzerland is estimated to hold about a quarter of the world's offshore wealth. Germany's refusal to say which bank's data are involved adds to the pressure.