The bank has been under investigation for several months, after allegations emerged that third-party pension fund managers had been paid kickbacks to sell their funds' shares in Swissbank ahead of the merger, meaning that their funds did not benefit from the share price increase which followed the alliance.

In late August, Thomas Matter tendered his resignation, announcing that:

“On account of the campaign that has been waged against my person with increasing intensity for some time now, and after giving this issue a great deal of thought, I have decided to step down prematurely from my mandate as CEO of the Swissfirst Group."

He continued:

"In doing so, I am surrendering my life’s work, a step which I find extremely difficult to take. I also appreciate the fact that I have the solidarity and unconditional backing of the entire Board of Directors. However, I see myself compelled to take this step in order to enable the Swissfirst Group and its employees to continue their business operations free from any polemics surrounding my person and any pending litigation and in order to protect my family."

Mr Matter's resignation statement concluded:

"I am deeply convinced that all transactions and acts that took place as part of the merger between the Swissfirst Group and the Bellevue Group were conducted within the scope of the applicable laws and legal standards. I plan to safeguard my rights as a private individual and will use all the means at my disposal to defend myself against attacks on my personal integrity.”

Last week saw the arrest of a pension fund executive at electronics firm Siemens, the first so far in the case.

Meanwhile, speaking to reporters this week, Swissfirst chairman, Martin Bisang denied that any kickbacks or illegal payments had ever been made to pension fund managers.