Spanish police have arrested a former HSBC IT worker who prompted a tax evasion scandal when he leaked the details of thousands of the bank's Swiss private banking unit's customers.
French national Herve Falciani now faces extradition to Switzerland, where in 2015 he was sentenced to five years in prison for industrial espionage.
In 2006 or 2007, Falciani, an IT employee at HSBC's Geneva-based private bank, stole details of thousands of customers.
Falciani fled to France while under investigation where in 2009 authorities acting on a Swiss warrant, seized the data from his home. However, rather than extraditing him, the French, and later the Italians and Spanish, began using the data to take on tax evaders.
Falciani later moved to Spain, where police received a Swiss international arrest warrant in March, prompting his arrest.
Swiss authorities says Falciani planned to sell the stolen data but he insists that he is a whistleblower exposing a banking system which "encouraged tax evasion".
In November, HSBC agreed to pay EUR300 million to French authorities to settle an investigation into tax evasion by French clients via Switzerland.