By Elisabeth O'Leary and Inmaculada Sanz

MADRID (Reuters) - Spain's Princess Cristina, daughter of King Juan Carlos, was charged on Wednesday in a corruption inquiry against her husband, the latest in a spate of high-level graft cases that have angered Spaniards suffering in a severe recession.

The princess, 47, was ordered to appear before a judge on April 27, charged in a pre-trial investigation amounting to an extraordinary legal move against a member of the royal family.

Judge Jose Castro said there was evidence the princess was an accomplice to her husband, Inaki Urdangarin, who has been accused of tax fraud and embezzling 6 million euros in public funds when he headed a charitable foundation.

"The law is the same for everyone," the judge said in a court document explaining his decision, echoing the king's own words in his 2011 Christmas address to the nation.

Corruption experts said Castro was building up to issuing a formal indictment against both Urdangarin and Cristina that could lead to putting them both on trial.

Disenchantment with the rich and powerful has grown in Spain as unemployment has soared to 26 percent, one of the worst rates in Europe, and a cases of corruption and nepotism in the ruling classes have piled up.

Manuel Villoria, an expert in corruption and professor of political science at King Juan Carlos University, called the charges "devastating" for the royal family.

"He is saying he considers (Cristina) an accomplice, that he (Urdangarin) could not have done it without her. She had knowledge and didn't put a stop to it," Villoria said.

The decision will probably deepen public disenchantment with the royal family and fuel debate on whether the once-popular king should abdicate in favor of his son, Crown Prince Felipe.

Castro had been looking into emails which were sent by Urdangarin to his wife asking for her advice on business matters at his charitable Noos Foundation.

A former Olympics handball player, Urdangarin is accused of using his powerful connections to win public contracts to stage events on the Mediterranean island of Mallorca and elsewhere in Spain. Urdangarin has denied any wrongdoing.

Castro said he had charged Princess Cristina because he wanted her to testify in person, and under Spanish law she could have avoided doing so had he charged her as a witness.

The Royal Palace declined to comment.

King Juan Carlos, 75, and his wife, Queen Sofia, have tried to distance themselves from the scandal. Urdangarin has been barred from royal family events, and photographs of him have been taken off the official website.

"I think this is a good thing. If she did something wrong, it's logical that justice be done," said Diana Presa, a student in Madrid.

In an unrelated case that has also stirred public ire, judges have brought charges against three former treasurers of the governing People's Party for crimes ranging from bribery to money laundering to tax evasion.

Public irritation with the king has risen as his luxury lifestyle, rumors of adultery and allegations of corruption in the royal family have taken prominence in once respectful local media while ordinary Spaniards face a crippling economic crisis.

Juan Carlos was once revered for his role in shepherding a transition to democracy in the 1970s after dictator Francisco Franco died. But his image has deteriorated.

Last year he broke his hip while hunting elephants on safari in Africa, and the news enraged many Spaniards whose standard of living has plunged during the recession.

In December a survey found 79 percent of Spaniards felt that Prince Felipe was ready to be head of state, while the king's personal approval rating had fallen to 58 percent, down from 74 percent before his safari.

The latest CIS poll showed Spaniards naming corruption as the nation's second biggest problem after unemployment.

(Additional reporting by Emma Pinedo and Fiona Ortiz, Editing by Julien Toyer and Mark Heinrich)