The list of Swiss firms signing non-prosecution deals with US regulators over secret accounts grows almost by the day.

Bank EKI Genossenschaft is the latest Swiss bank to reach such an agreement under the terms of a US-Swiss treaty signed in August 2013. The bank, founded in 1852, “opened, serviced and profited” from accounts for US clients with the knowledge that many were likely not complying with their tax obligations, according to the US Department of Justice.

Many accounts were transferred from other Swiss financial institutions that were closing such accounts and Bank EKI knew "or had reason to know" that a portion of the accounts were probably undeclared for tax purposes, the Americans added.

Since 1 August 2008, Bank EKI has held a total of 64 US-related accounts with slightly more than $21 million in aggregate assets.

The US-Swiss treaty of August 2013, which calls itself a 'programme,' allows Swiss banks to offset various criminal charges they may incur in the US. Once it was in operation, banks were told to tell the Department of Justice by the end of December 2013 whether they thought that they might had committed tax-related criminal offences. Some stated that they had no reason to believe that they had broken any US laws. Banks already under investigation were excluded from the deal.