Ana Botin, head of the Spanish banking giant Santander’s UK operations, has been plunged into an investigation over her tax affairs, in particular money deposited with HSBC Private Bank in Switzerland, the Evening Standard reports.

The investigation was initiated following the highly publicised theft of client data from HSBC Private Bank (Suisse) which came to light last year, the Madrid national court is reported to have said in a statement. It is thought that the French authorities alerted their Spanish counterparts to possible irregularities with a number of Spanish client accounts at HSBC’s Swiss private banking unit. The probe is believed to encompass eight other members of Botin’s high-profile banking family, including the chairman of Santander, Emilio Botin, of whom Ana is the eldest daughter.

The investigation into Botin apparently concerns unpaid taxes in the region of €120,000 ($169,000). The broader investigation is focusing on income not properly reported in the period between 2005 and 2009.

The Botin family has issued a statement saying it had voluntarily regularised its tax affairs and is in compliance with all its tax obligations, the report said.

Santander had not responded to enquiries on the matter from WealthBriefing at the time of publication.

In October of last year news emerged that Spain’s tax authorities were stepping up the pressure on some 1,500 clients of HSBC’s Swiss private bank to declare €6 billion (around $8.4 billion) of funds held offshore and had given them until the end of the month to comply or face prosecution.

The affair highlights the issue of how far governments can and should go in using stolen data to track down illicit funds. The German government, for example, has paid for data that had been stolen from private banks in recent years.

Hacienda (the country’s tax office) originally wrote to clients of the bank in June 2010 demanding they regularise their affairs after the now notorious data theft perpetrated by the former HSBC employee Herve Falciani. Falciani is alleged to have stolen details on thousands of account holders of various nationalities while working within the bank’s IT department and subsequently fled to France to escape the attentions of Swiss investigators.

According to the reports, Hacienda’s initial letter was largely ignored by the clients in question, prompting the tax office to announce that individual tax inspections would be taking place in August and September. This produced cooperation from an “appreciable number” of the account holders, according to reports, but a large proportion still chose to ignore the warnings in the belief that the stolen data may prove to be inadmissible in court.