Amid a political storm about the Hong Kong/London-listed banking group’s private banking activities, authorities in Switzerland, and elsewhere, are scrutinizing claims that thousands of accounts of alleged tax dodgers were held by HSBC in the Alpine state.

In 2006, a former employee of the bank, Hervé Falciani, removed a cache of client account data and has been prosecuted in Switzerland for attempting to sell it. He claims he acted in good faith as a whistleblower but Swiss authorities say his acts were criminal and in clear violation of decades-old Swiss bank secrecy law.

Last week, the BBC Panorama TV program described how the bank allegedly aided thousands of tax dodgers; the bank has responded by saying that, since 2008, thousands of accounts have been shut down and the amount of money held in the private bank in Switzerland has been sharply reduced. It is understood that some of the accounts were closed as far back as the early 1990s before the private bank entity was even under HSBC’s ownership. However, groups such as UK legislators still insist that not enough has been done to punish wrongdoers and have chided the UK tax authority, among others, for not acting aggressively or quickly enough.

Asked about the reports of the Geneva prosecutor’s search, a spokesperson for HSBC told this publication: "We have cooperated continuously with the Swiss authorities since first becoming aware of the data theft in 2008 and we continue to cooperate."

Media reports quoted the prosecutor as saying: “A search is currently under way in the premises of the bank, led by Attorney General Olivier Jornot and the prosecutor Yves Bertossa."

Stuart Gulliver, the chief executive of the banking group, wrote a full-page apology in several weekend newspapers in the UK about the matter; the bank has also issued a long statement about the matter.

As well as raise the issue of how governments continue to chase alleged tax dodgers, the case also highlights how there is often a grey area between avoidance and evasion . The use of stolen data as a basis for any prosecutions of tax dodgers also raises questions about due process of law. Switzerland has entered information sharing and tax disclosure pacts with a number of countries, such as in 2013, when it signed an agreement with the US over offshore accounts.