Spanish Princess Is Subpoenaed in Embezzlement Case Involving Her Husband

King Juan Carlos, as part of a widening investigation into whether her husband embezzled millions of euros from a sports charity, further tarnishing the image of the monarchy at a moment when corruption cases have shaken the foundations of virtually every public institution in Spain.

In naming Princess Cristina as a suspect, the court sundered efforts by the royal household to limit the damage of the investigation into the dealings of her husband, Iñaki Urdangarin. He first appeared in court in February of last year and has already been sidelined from any involvement in royal affairs.

The decision by José Castro, the Palma-based judge leading the case, has created an unprecedented opening for the corruption investigation to enter the palace, making Princess Cristina the first royal-born person to be called before court in modern Spanish history. Mr. Urdangarin, a former Olympic handball player, comes from a wealthy Basque family but was not part of the nobility until he married the princess.

Under Spanish law, the king is the only member of the royal family to benefit from complete immunity from prosecution. As such, Judge Castro said that not summoning Princess Cristina would have run contrary to the principle that justice treats everybody equally.

Judge Castro said in a filing that there was enough evidence to believe that the princess knew that her husband had been using her name and status to further his suspect business deals. Prosecutors have been investigating for more than two years whether Mr. Urdangarin used his royal credentials to secure inflated sports contracts from regional politicians for Instituto Nóos, a foundation that he chaired, before then siphoning off millions from the contract fees toward other companies and offshore accounts that he and his associates controlled.

The judge said that his decision was partly motivated by the content of e-mails recently supplied by Diego Torres, the main former business associate of Mr. Urdangarin. Mr. Torres is asserting that Mr. Urdangarin made no move without palace approval and that Princess Cristina, as a board member of two of her husband’s companies, was among those kept most closely in the loop. She is set to appear in court on April 27.

A spokesman for the royal household said on Wednesday that it was “surprised” by the change in the stance of Judge Castro, who had indicated in March of last year that there was not enough evidence to name the princess as a suspect. The royal household also said that it would back an appeal lodged Wednesday against the judge’s decision by the main prosecutor for the case, Pedro Horrach, who argued against naming Princess Cristina for lack of evidence.

Mr. Urdangarin’s own lawyers recently asked the court to remove from the evidence the e-mails that had been provided by Mr. Torres to back his claims that the king, Princess Cristina and others in the royal household had monitored Mr. Urdangarin’s activities long before had been publicly acknowledged by the royal palace.

Mr. Urdangarin has denied any wrongdoing, and he and other suspects have not been charged with any crime. In February, he also denied that the king, Princess Cristina and other members of the Spanish royal household had any direct involvement or even offered him any advice relating to the sports foundation. Mr. Urdangarin became Duke of Palma in 1997 upon marrying the king’s youngest daughter.

The scandal involving the palace joins a lengthening list of corruption investigations that have undermined Spaniards’ confidence in their governing institutions and stoked popular resentments at a time of grinding economic hardship for many.

Another graft scandal has recently also landed on the doorstep of Prime Minister Mariano Rajoy, focusing on how his governing Popular Party’s former treasurer, Luis Bárcenas, amassed millions in secret Swiss bank accounts. Prosecutors are also investigating allegations that Mr. Bárcenas ran a secret fund to make illegal payments to Mr. Rajoy and other senior conservative politicians.

While Mr. Rajoy and other party leaders have denied wrongdoing and the existence of such a slush fund, the allegations have recently helped sink Mr. Rajoy’s popularity to its lowest level since he came to power in late 2011, particularly as crisis-hit Spaniards have been struggling under austerity measures imposed by the government.

As a result, during recent protests held in Madrid and other cities, demonstrators have been shouting slogans like “Your envelopes, my spending cuts!”

While such spending cuts have helped reduce Spain’s bloated budget deficit, Spain ended last year with a deficit of almost 7 percent of gross domestic product, compared with the 6.3 percent that it had agreed with its European counterparts, according to data released last week by Madrid.

Meanwhile, the king’s own popularity has slumped as a result of his own mishaps. Last year, Juan Carlos issued an unprecedented apology after injuring himself on an African elephant hunting vacation that was seen as an affront to the belt-tightening endured by ordinary citizens.

Supporters of the monarchy worry that the corruption case involving the king’s daughter will make matters worse for the palace. According to an opinion poll published earlier this year by El Mundo, a conservative newspaper, almost 45 percent of respondents said they would want the aging king to abdicate in favor of his son, Crown Prince Felipe.