A former employee of the Basel cantonal bank (BKB) has asked Switzerland’s financial regulator to investigate the bank over management improprieties, according to a newspaper report.

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The Aargauer Zeitung on Tuesday reported that a former employee of BKB’s Zurich branch contacted the Swiss Financial Market Supervisory Authority (Finma) for an audit of the bank.

The cantonal bank’s CEO Hans Rudolf Matter stepped down in October following a scandal involving foreign exchange trading at its ASE subsidiary.

Finma withdrew ASE’s trading licence after more than 500 investors lost more than 100 million francs, by BKB’s own estimates.

The financial authority launched an investigation into the FX company last May, stating that the investors, who were promised “very high returns . . . were victims of business practices that are the subject of ongoing investigations”.

“The case of the alleged ASE investment scam is just the tip of the iceberg,” the whistle-blowing former employee, who wishes to remain anonymous, told Aargauer Zeitung.

He alleges “unauthorized bond, equity and foreign exchange trading” by the bank in addition to its involvement with “aiding capital flight” and “dubious investment vehicles”, which he maintains were known to top management.

The cantonal bank in October issued its own report based on the independent review of a law firm that it acknowledged showed a “shocking picture” of the ASE activities.

But it also blamed weak supervision by employees at its Zurich branch, three of whom were let go, while a further four were given warnings.

The whistleblower was apparently one of those fired, although he alleges he made an enemy of the Zurich branch manager by earlier reporting his concerns to the bank’s legal branch, the Aargauer Zeitung says.

He denies seeking revenge against his former employer.

The cantonal bank has publicly stated that it took measures to improve internal operations and correct admitted mistakes in the wake of the ASE debacle.

A spokesman from Finma told Swiss media it will review the information it has received but that it cannot comment on the details.