In a statement, anti-corruption prosecutors said BBVA was suspected of "bribery, breach of confidence and corruption in business."

The judge in charge of the case at Spain's National Court, which handles major financial cases, must now decide whether to charge the bank or not.

Earlier this month, nine former or current managers at the bank were put under formal investigation in the same case.

BBVA is suspected of having used Jose Manuel Villarejo, a now retired police superintendent, to illegally tap the phones of journalists, politicians and businesspeople to push back an unwanted shareholder, according to Spanish media.

In January, the bank admitted it had previously used the services of a business intelligence group called Cenyt and had launched an internal probe into the issue.

Cenyt was linked to Villarejo who is currently in jail, suspected of having done dirty work, such as blackmail or threats, on behalf of companies or rich individuals for decades.

For years, he also recorded conversations with the all-powerful and has been drip-leaking these from prison, striking fear among high-profile politicians, business leaders and even the monarchy.

Among those probed in the BBVA case is Angel Cano, who as chief operating officer from 2009 to 2015 acted as deputy leader of the bank.

In January, BBVA said it had not "found any paperwork reflecting any monitoring or tapping of private communications" in its initial internal probe.

But the case still forced Francisco Gonzalez, who as executive chairman of BBVA was its top leader, to resign from all his posts, including honorary ones, by March 2019.