Spain's National Court agreed Wednesday to open an investigation into the former management of recently nationalized Bankia, naming as suspects the ex-chairman of the banking conglomerate, Rodrigo Rato, and more than 30 of its erstwhile board members.

Judge Fernando Andreu made the decision after the anti-corruption prosecutor's office found that a suit filed by the small Union, Progress and Democracy, or UPyD, party over alleged fraud and other crimes merited investigation, judicial officials said.

Bankia, Spain's fourth-biggest financial institution, was nationalized in May and it subsequently announced that it would seek an additional 19 billion euros ($23.8 billion) in state aid, or the largest bank bailout in Spanish history.

Created from the merger of seven ailing regional lenders, Bankia was one of the banks hardest hit by the 2007 collapse of a long-building real-estate bubble.

Former board members of Bankia and parent holding company Banco Financiero y de Ahorro, or BFA, named as suspects in the case include Jose Luis Olivas, ex-chairman of Bancaja, and Angel Acebes, former justice and interior minister in Prime Minister Jose Maria Aznar's 1996-2004 administration.

The UPyD party, headed by former Socialist lawmaker Rosa Diez, filed the complaint against all sitting board members of Bankia and BFA at the time of last year's initial public offering of Bankia SA.

Rato, who served as managing director of the International Monetary Fund from 2004 to 2007, resigned as chairman of Bankia on May 7 and was replaced by Jose Ignacio Goirigolzarri, a former executive of BBVA, Spain's second-largest bank by market value.

BFA-Bankia was nationalized two days after the departure of Rato, who took over as chairman of Caja Madrid in January 2010 and soon afterward announced that institution's merger with six other savings banks to create Spain's leading banking group by business volume.

The Bankia subsidiary was created with the aim of listing the group's most attractive assets on Spain's stock exchange, while the banks' toxic assets were transferred to the BFA holding company.

Rato had earlier served as deputy prime minister in Aznar's administration and economy minister during a period of strong growth in the late 1990s and start of the 21st century.

The suit accuses Bankia's former management of falsifying accounts and balance sheets, dishonest and fraudulent administration, stock price manipulation and embezzlement.

Spanish law establishes prison terms of between one and three years for falsifying accounts; six months to four years for fraudulent administration; six months to two years for stock price manipulation; and one to six years for embezzlement.

The National Court, which handles high-profile cases in Spain, claimed jurisdiction in the case because the alleged crimes may have had "serious repercussions in the national economy."

The judge said Bankia was the country's fourth-largest bank with total business volume of more than 485 billion euros ($608 billion) at the end of 2011 and that therefore its "bankruptcy could destabilize the country's entire financial system."

The 19 billion euros ($23.8 billion) in state aid requested by Bankia are in addition to a loan of 4.46 billion euros ($5.6 billion) - converted into shares earlier this year as part of the nationalization process - the group received in 2008.

That brings the total cost to public coffers to 23.46 billion euros ($29.4 billion), the judge said.

Among those named as witnesses in the investigation are the former Bank of Spain Gov. Miguel Angel Fernandez Ordoñez, who stepped down from his post in June - a month ahead of schedule - amid sharp criticism of his handling of Spain's financial crisis.

The Iberian nation's economy has been battered in recent years by the global recession and the collapse of a massive real-estate bubble, which has left banks saddled with toxic property assets.

The overall unemployment rate stands at almost 25 percent and nearly half of Spaniards under 25 are jobless, while tens of thousands of families have been evicted from their homes after falling behind on their mortgages.

Euro-zone finance ministers last month agreed to extend a lifeline of up to 100 billion euros ($125 billion) for troubled Spanish banks. EFE