Spain's Princess Cristina, daughter of King Juan Carlos, was charged today with association in a corruption case involving her husband, and ordered to testify before a judge in an unprecedented court order against a member of the royal family.

Judge Jose Castro wrote in his order there was evidence the princess cooperated with her husband, Inaki Urdangarin, who has been accused of embezzling 6 million euros in public funds and tax fraud when he headed a charitable foundation.

The Royal Palace declined to comment. Urdangarin has denied any wrongdoing. Cristina is due to appear in court on April 27.

Judge Castro had been looking into emails which were sent by Urdangarin to his wife asking for her advice on business matters. A former Olympics handball player, he is accused of using his powerful connections to win public contracts to put on events on the Mediterranean island of Mallorca.

Public irritation with the 75-year-old king, long admired for his role in restoring democracy, has mounted as his luxury lifestyle, rumours 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.