PARIS — Princess Cristina, the younger daughter of King Juan Carlos of Spain, was formally accused of money laundering and tax fraud by a magistrate on Tuesday and was summoned to appear in court on March 8. She is the first close relative of a Spanish monarch in modern history to face the prospect of a criminal trial.

The accusations arise from a long-running corruption investigation that has also ensnared the princess’s husband, Iñaki Urdangarin, a businessman and former Olympic handball player who is fighting charges of fraud, tax evasion and embezzlement. Both the princess and Mr. Urdangarin, who has been accused of embezzling 6 million euros, about $8.2 million, in government money though a foundation he set up to organize sports conferences, have publicly denied the charges.

José Castro, an examining magistrate from Palma, Majorca, lodged the accusations against the princess in a 200-page ruling.

The widely publicized investigation has badly dented the standing of the royal family with the Spanish public. In a new poll by Sigma Dos, a broad majority said they believe the monarchy mishandled the case, and many of them said they think the king, who is 76, should abdicate.