Whistleblowers allege failed bank helped rich Americans evade taxes in bombshell claims

Credit Suisse, the failed Swiss bank that was just purchased by the UBS Group, has a history of facilitating tax evasion in the United States — but a pair of whistleblowers say it has been continuing for years after regulators and prosecutors thought they had stamped it out, reported CNBC on Wednesday.

"For years, the private bank has provided a safe haven for wealthy American clients to hide assets from the IRS — even after it was caught and prosecuted for doing the same thing more than a decade ago, according to two former Credit Suisse bankers who spoke in exclusive interviews with CNBC and are working with the U.S. government as whistleblowers," reported Eamon Javers.

As part of a plea deal in 2014, Credit Suisse "admitted ... that it used sham entities, destroyed account records, and hand delivered cash to American clients to avert IRS detection — agreeing to crack down on U.S. tax dodgers going forward as part of its plea deal. Credit Suisse also agreed at the time to a host of reforms, including disclosing its cross-border activities and cooperating with authorities when they request information, among other things."

According to these two executives, however, Credit Suisse has been violating this agreement — and Senate investigators say that the bank "enabled as many as 25 American families to hide fortunes totaling more than $700 million in the bank in the years after the bank’s plea agreement."

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Even before the current banking instability, Credit Suisse was on regulators' radar, with authorities last year considering stripping it of the right to managing pension fund assets in the United States.

Amid the bank's failure, the Swiss National Bank poured $100 million of liquidity into it and "agreed to provide UBS with some $9 billion to backstop losses resulting from the takeover," according to the report.

However, this revelation could put UBS on the hook for some of Credit Suisse's new legal liabilities. According to lawyers representing the whistleblowers, UBS could be responsible for paying up to $1.3 billion to settle the new tax evasion claims.