By Miles Johnson in Madrid

Emilio Bot?n, chairman of Banco Santander and one of Spain?s highest profile public figures, is being investigated by the country?s high court over allegations of tax-related offences alongside 11 other members of his powerful family.

The court said on Thursday it was carrying out an investigation related to information provided to the Spanish

authorities by French tax investigators about Spanish clients of HSBC?s Swiss private bank who had misreported income during the period from 2005 to 2009.

The court said that it had to make a formal notification of the investigation to keep the case open before the 2005 year falls under Spain?s statute of limitations in July. No specific charges have been brought against the Bot?n family.

During a tax amnesty last year for undeclared accounts at the HSBC Swiss private bank, the family voluntarily paid 200m euros ($283m) to settle an outstanding tax bill over an account that is the focus of the investigation, according to people familiar with the matter.

The probe includes Mr Bot?n, his brother Jaime and their combined 10 children, who include Emilio Bot?n?s daughter Ana Patricia Bot?n, chief executive of Santander UK.

One person close to the situation said that the investigation related to an account set up in 1937 by Emilio Bot?n Snr, the Santander chairman?s father who died in 1993. He used the account to store part of the family?s wealth when he left Spain for London during the Spanish civil war. The account was left dormant with no funds taken in or out since the death of Mr Bot?n Snr, according to one person close to the situation.

The account came to the attention of Spanish tax authorities in 2010 during an investigation into 659 Spanish accounts of HSBC?s Swiss private bank.

Jesus Rem?n, lawyer for the Bot?n family, said: ?The family has voluntarily and completely normalised its fiscal situation and is up to date on all tax obligations. It hopes that this matter can be satisfactorily and quickly clarified by the court.?

Fernando Andreu, the investigating judge, said: ?Due to the impossibility of evaluating the [high volume of] declarations [provided by the Bot?n family] within the time period, the investigation is necessary?.

The judge said that if the declarations provided by the Bot?n family were satisfactory, the case would be thrown out.

? The Financial Times Limited 2011