The new chief of Santander UK and her family are facing a tax evasion charges by a Spanish court.

Just six months after she was named to head the bank, Ana Botín and eleven family members -- including her father Emilio Botín, the chairman of Spanish banking group Banco Santander S.A. -- are accused of not paying taxes.

Santander UK is a British unit of Banco Santander.

The case apparently relates to a trust account established by Emilio’s deceased father with HSBC Switzerland in December 1936, when the elder Botin fled the Spanish Civil War and moved to London. According to reports, the Botín family has already paid 200-million euros to settle the tax outstanding on the trust.

However, when tax records of HSBC’s Swiss private banking clients were leaked by a former employee, it led to a probe of more than 600 Spaniards with accounts at the British bank, including the Botins.

In a statement, the Botin family said it did nothing wrong and will be exonerated.

"The family has voluntarily and completely normalized its tax situation and is compliant with all obligations. It expects this matter to be quickly and satisfactorily resolved by the court," a lawyer for the Botíns said.

Mauro Guillen, a professor at the Wharton School of the University of Pennsylvania in Philadelphia, told Bloomberg: “There is suddenly uncertainty surrounding the management of a bank that is very closely associated with a single family and that is clearly a concern.”

The Botins are one of the most powerful and influential families in Spain. Santander UK is now one of the five biggest retail banks in Britain and might be listed on the London exchange later this year.

Earlier this year, Santander's chief executive Alfredo Sáenz was sentenced to prison and banned from the banking industry by Spain’s national court for fraud and making false claims. Saenz has appealed the ruling.