Spain's High Court on Tuesday rejected a second extradition request from Switzerland against Herve Falciani for leaking details of thousands of clients of HSBC's private bank.

Hailed as a hero by some for triggering tax evasion investigations in several countries by leaking details of HSBC clients, Swiss courts sentenced Falciani, a French citizen who worked for the bank, in absentia to five years in jail.

The Spanish court denied the extradition request over alleged industrial sabotage by Falciani in 2008 because the charges in the Swiss ruling are not considered a crime in Spain.

"The Spanish Criminal Code does not include any charge similar to the crime of 'aggravated financial espionage' for which the Swiss justice had sentenced Falciani to a 5-year prison sentence," the court said on Tuesday.

Last week, Falciani told an extradition hearing that he had helped other countries uncover tax frauds.

Spanish courts and anti-corruption prosecutors have played a key role in such investigations by passing on information that originated from Falciani.

France, Austria, Belgium, Spain and Argentina launched investigations based on the leaked data, but Swiss authorities insist it was stolen and therefore legally inadmissible.

APPEAL POSSIBLE

The Spanish prosecutor said last week that charges were different in both countries and that the information Falciani collected from HSBC was never transmitted to private individuals, but only to official organisations.

The Spanish ruling can be appealed within three days, although Switzerland's Federal Office of Justice, which lodged the extradition request, declined to comment on it.

If Switzerland were to appeal, a special section of the High Court would rule on it, but the Spanish government would have the final say as extradition requests are usually submitted to the Justice Ministry.

Falciani was arrested in Madrid in April while on his way to speak at a conference on whistleblowing. Spain's High Court released him the next day, but ordered him to remain in Spain while the extradition request was considered.

Falciani had been detained once before in Spain on Switzerland's request - on a trip in 2012. He was released after the High Court ruled against his extradition.

On Tuesday, the Spanish court said Switzerland's extradition request was identical to that of March 2013 and it deferred to the previous rejection in its ruling.